License added to Date.h. Empty Time class files added.
Changed DateTime class role to provide supporting functions to Date and Time class. Will later be set up as a first class class that has a Date and a Time as attributes and these will be synchronised to store a single DateTime instant. Fixed int data type issues. Classes use int that are defined short when not in ARDUINO environment. main() uses a define to revert the int > short definition to leave int as it's normal 4-byte type.