Release covering versions from 8 to 12

Features:

• stored GCode programs
• pause GCode when spindle stops
• receive keycode events over Serial

Fixes:

• hardware pulse counter for spindle encoder helps filter extra pulses
• fix bug in async mode position when moving left
• fix setting X0 from diameter when position is not 0

Code diff: https://github.com/kachurovskiy/nanoels/compare/H4V7...H4V12

Fixed the wrong free move speed during tuning/facing/auto-threading.

Features:

• Show distance between limits when starting the operation.
• Show distance to start point when starting the operation.
• Implement "Internal" ellipses as having same start/end points as "External" but concave.
• Entering diameter and pressing A sets X0 as -diameter/2.

Fixes:

• Limit GCode minumum speed 1mm/min.
• Fix "1 passes" line.
• Fix repeated enabling/disabling on A1 during manual move.
• Fix displaying of the "key pressed on start" emergency stop state.
• Fix problem with stuck CUT when left limit is set on current Z.

Cleanup:

• Address all compilation warnings.
• Use const instead of #define for configuration values to avoid #define pitfalls.
• Increase default X manual move speed.
• Decrease default Z acceleration.