FIXED FREEZING AddDecimal Issue

Program could sometimes freeze whilst performing string functions AND
the SD card is inserted (no idea why).
This change seems to fix it though, and makes the code simpler.
2 Changes

I allowed CheckDrillLock function to return 2 cycles  - for the case
that one was skipped.
I implemented battery fail checking and protection, as the driver
circuit burns out if the motor is attempted to be run while the battery
dies.
Fixed bugs