Fixups for power-loss, whitespace

[thinkyhead]

• Remove all trailing whitespace.
• Replace tab indentations with spaces.
• Add standard power-loss test G-codes.
• Wrap some pins-dependent code in conditionals.
• Organize power-loss detected / resume / set-mix code into functions.

To see only the non-whitespace changes: Concise Diff.

[thinkyhead]

In testing I still see one issue with this (on A10M and A20M). The power-loss recovery file ("BIN") is not deleted (or zeroed) at the end of the print job. I will post the solution if I find it first.