Changes for easier support and tweaking

* Added printStats() to print stats even without debug
* Added serial message function DebugPrint to save some memory
* Added serial listener to enable temporary changes to drift offsets (very simple implementation). 
For example, in Arduino serial monitor type x2.2 and then press Enter to change the xDrift compensation. 
Due to memory, only loaded when debug is turned off
* Tried to remove overloaded serial prints (convert Floats to Char first) but would have to do every one to save any memory so I just commented out the examples I started with using dtostrf
* Moved 3 variables to smaller types, identified with comments //was long or //was unsigned long