See #11097

* Fix G29 (ABL) retry behavior

To allow for the case where a Z endstop (e.g., hall effect) is higher than the probe trigger point, don't check the Z min endstop during probe moves. See #11134

- Allow planner to alter the deceleration phase of the currently executing block.
- Remove BUSY flag, as it is NON ATOMIC to set bits in the Stepper ISR and Planner at the same time.

Co-Authored-By: J.C. Nelson <xc0000005@users.noreply.github.com>

Fixed for cycle used to initialize default values

...and recommended pulse width configuration for A4988

Co-Authored-By: p3p <p3p@p3psoft.co.uk>

* Planner: Removal of some race conditions between Stepper ISR and Planner, some of them pointed out by @AnHardt, some of my own findings
* Fixing timing on stepper pulses adding a compensation for the non-null time required to set ports.

See https://github.com/MarlinFirmware/Marlin/pull/11079#issuecomment-399309709

-Enable boards_dir option in PIO INI
-Remove defunct custom board file operations for PIO auto-build environment
-Remove now-defunct Teensy++ 2.0 PIO entry, replaced by `at90USB1286_DFU` and `at90USB1286_DFU` (using this entry always put AT90USB board boot loaders in jeopardy of being overwritten due to the very small size of the official Teensy++ 2.0 bootloader)
-whitespace

According to https://github.com/MarlinFirmware/Marlin/issues/9917#issuecomment-399204568

[2.0.x] Fix value editing (with callback)

See https://github.com/MarlinFirmware/Marlin/issues/5597#issuecomment-397683325

The registers within the Max7219 can get corrupted a number of ways.  This allows the Max7219 to be reset and fully initialized.
And...  it also allows the user to see the initialization pattern.

Fix message to long for 12864 display