Fixes gCode handling of comments and escaped characters

Fix compile error in gcode_G29

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

Minor typos in the README

Undubble MSG_MIN & MSG MAX

In-line comments and escaping fixed by foosel

  * "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 ")"

Gcode handlers to inline functions

Enhanced G29

Latest upstream changes

Fix autoretract

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

Sync with upstream

Add support for solenoid articulated extruders

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

Cleanup rotary encoder encrot* defines

- 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 X_Axis could not home to min while Y_Max endstop was trigged.

Cleanup of cardreader.*

- Apply standards to cardreader.*
- Fix minor issues with cardreader.cpp
- Apply standards to some other stale regions

The encrot values are used in only one place, and don’t vary, so remove
redundant references.

Cleanup of temperature code

Fix undefined *_PROBE_BED_POSITION error

Panel One encoder pins

Merge upstream changes

Added support for PanelOne from T3P3.

Extend the idea of dummy temperature sensors.

Support for simple customisable AutoZProbing area

- Reduce calls to millis()
- General cleanup of manage_heaters
- General cleanup of pid autotune
- Formatting here & there
- Macros to clean up and shrink ISR code (reduced by ~364 lines)

Added a second sensor and made them configurable.

Cleanup and fix ultralcd.cpp