this PR replaces some bools with one char. this will safe 3 bytes and should also be sometimes a little bit faster.

ok N(linenumber) P(bufferremaining)
the host can use this to send the data much faster.

Some pseudo code:
If (bufferremaining > 0)  send command
## as long there is free buffer send command

Also
if (linenumber > lastsend - bufferremaining) send command
## as long last linenumber received is bigger than lastsend (host) - last bufferremaining received

This reverts commit 22e0d2afcb.

Persistent homing message.
Message was declared as an alert, therefore it was persistent.
Updated to message.

This reverts the changes done to the error message for line number mismatches done in commit d43cc2dd5f

Servo.cpp and Servo.h were changed to lowercase in Makefile but not their actual filenames.

- Also move audio feedback into the command
- Added shorthand for `lcd_buzz` availability

in all Configurations.

Add `sync_plan_position()` after `axis_is_at_home(axis)` to keep the
planner position in sync when homing.

This makes `M421` more amenable for irregular matrices

Updated "servo.h" to "Servo.h"

Corrected "servo.h" to "Servo.h" because of the updated filename.

- Add “Level Bed” menu item for auto bed leveling
- Hide the option if homing has not been done yet
- Arrange the Prepare submenu more logically (?)
- Add documentation comments, some white-space
- Apply some coding standards here and there
- Move old encoder multiplier debug option to `ultralcd.cpp`