- A redo of #1576, which missed topo_flag
- Always set verbose_level

add ```^ !(n_ENABLE_ON)``` for each stepper

  * "G1 X1 ; test" was not executing "G1 X1" due to never leaving comment mode.
  * "M117 Hello \;)" printed "Hello \" to the display due to not replacing serial_char properly.

Tested with the following commands:
    * M117 Hello ; test => displays "Hello" on display, ignores "test"
    * G1 X1 ; foo => moves 1mm in X, ignores "foo"
    * ; test => completely ignored, not even acknowledged
    * M117 Hello \;) => displays "Hello ;)" on display
    * M117 Hello \\;) => displays "Hello \" on display, ignores ")"

Autoretract was broken, looks like it was overlooked when the retracted flag was updated for multi extruders.

- Setting boundaries based on configured limits, contrasting with G28
(which forgets these limits?)

- Adapted “Enhanced G29” code referred to in #1499 and posted at
[3dprintboard.com](http://3dprintboard.com/showthread.php?3105-Auto_Bed_
Leveling-Enhanced-G29-command)
- Compatible with current G29 while adding some new arguments
  - `V` sets the verbose level for serial out
  - `T` (or `V` > 2) send a Topology report to serial out
  - `E` works the same way as before
  - `P` works as before (source used `n` or `U`/`u`)
  - `L`, `R`, `B`, `F` work as before
- Still needs sanity checking for `LRBF`

The `float` keyword should not be on these vars because they conceal
the outer vars, preventing them from obtaining known values before
being passed in `set_bed_level_equation_3pts`. Possibly related to
`Z_RAISE_BETWEEN_PROBING` not functioning.

When probing PCB´s I had the problem that i needed auto-leveling for specific areas (it´s never the same size).
Not much code, but very useful.
Now I use simply G29 L5 R55 F5 B35 P3 to probe a 4x6cm PCB before milling.
I used int for values... might be wrong...
I hope this time I got the right development tree. (tried first with https://github.com/MarlinFirmware/Marlin/pull/1130/commits)

I've insert the define and pointer entries for the Viki 2 and miniViki
from Panucatt in all of the example configs and main config. With these
additions and with pins done in the old single pin.h style...I was able
to get the display working fine save for needing to turn Delta Segments
per Second down. But that's a common graphics lcd issue being looked
into right now.

I need assistance in understanding how the new divided pins files fit
together because my previous attempts at trying to get it to work
appropriately didn't seem successful. This originally came from trying
to find out how to swap the XYZ Min and Max Endstop pins in the Azteeg
X3 Pro. It only comes with one set of connectors and they're Min
Endstops. My previous experience didn't turn out well trying to tell the
firmware to home to the Min Endstops so the best solution I found was to
swap the pins in the firmware. If I'm missing a conflict with a setup
other than delta please let me know, but it makes sense in my setup.

- Patch from #1453 for delta movement plan
- Fix: Set X with code X instead of adding to X

Only a missing ","... now it will compile again

- Also partial cleanup of Marlin_main.cpp with a smidgen of Doxygen.

Update ConfigurationStore to always write dummy values for disabled
options, including FWRETRACT, DELTA, and SCARA. Update the EEPROM
version to “V15.” Also fixes a buffer overrun with axis_scaling in
Config_ResetDefault.

G29 E was not retracting the probe on the last probe point when used with ABL grid. Corrected.

* Adds config parameter `PID_PARAMS_PER_EXTRUDER` - allows single PID
parameters to be used where this would be preferable (e.g. dual
identical extruders)
* When disabled, will use `float Kp, Ki, Kd, Kc;` as before.
Preprocessor macros used to switch between.
* ultralcd.cpp defines extra menus for extra parameters only where
required
* M301 reports `e:xx` only if independent pid parameters enabled
* EEPROM structure still leaves space for 3 extruders worth, when undef
will save single parameter to all extruder positions, but only read the
first
* Switching off saves approx 330 B with no LCD enabled, 2634B with LCD
(RRD) enabled: this is significant.
* LCD modifications should be tested.

This change introduces an improvement to G29 command on Marlin.

Auto bed leveling operation's reliability is based on the repeatability of the Z-probe switch and the servo. This change introduces an option to G29 command. When the G29 command is sent with an "e" option, during auto bed levelling the servo is not retracted between probes which decreases the bias on auto bed levelling resulting from servo.

G29 command does the auto bed probing as it is.

G29 E command engages the servo on first probing point, probes all points and retracts the servo after probing the last point.

Please comment your opinions, test on your printer and check the code on a programmer's perspective. (I am not a good programmer.)

* Variables Kp, Ki, Kd, Kc now arrays of size EXTRUDERS
* M301 gains (optional, default=0) E parameter to define which
extruder's settings to modify. Tested, works with Repetier Host's EEPROM
config window, albeit only reads/updates settings for E0.
* All Kp, Ki, Kd, Kc parameters saved in EEPROM (version now v14), up to
3 extruders supported (same as Marlin in general)

try, try again.

If 'OK' is garbled on sending PC won't receive it.  Both machines will
wait on each other forever.  This resends OK if nothing is heard from PC
for a while to avoid this bad case.

fixed minor typo