Rename Decimal_Precision.h to decimal_precision.h
Update and rename Engine_Core.h to engine_core.h

I completed up to page 19 of the book, everything for the time being will be very closely related and almost identical since this is the basis and will not change much between any engine.
Command line is frustrating
I hate git right now
I really really hate command line
Finally working???
Merge https://github.com/TheSquishyDitto/Marballs

Conflicts:
	include/Engine_Core.h