add BLTouch-related messages in english and (rusty) french;
add missing endstops.h in ultralcd.cpp;
fix misc. compiler warnings;
fix lsf_reset - ZERO macro can't handle a pointer as it would only memset the size of the pointer, not the size of the entire struct

Right now G26 doesn't send a notice to the host that it's running.  It's
not until the heaters are at temperature that you know for sure if it's
running or not.

Added host temperature prints so that someone watching the host
interface will see the temperatures change during the warm up period.
Updates are sent every 5 seconds.

fix maximum mesh_index_ array size at 16 (15+1);

Pretty much...  The code is in place.  Still more work to do.    But it
has a lot of hooks and variables in other code, so commit and merge
before I pick up a million 'Conflicts'.

- Make all `unified_bed_leveling` data/methods static
- Move some UBL-related variables into the class
- Replace `map_[xy]_index_to_bed_location` with `mesh_index_to_[xy]pos`

The wait_for_user change totally broke UBL.   But there is stuff wrong
now in the thermal code and/or LCD Panel code.

The retraction flag in UBL's G26 was conflicting with the FWRETRACT option.

All fixed!