Base - expansion split, minor changes

- Implemented GameDefinition to differentiate between base game (RA2)
and expansion (YR)
- YR exclusive files are excluded if base game is loaded
- Implemented YR and RA2 count for Actions, Events and Script Actions
- Implemented Game tag in CONFIGS file to define what game is used
- New guidline; YR and RA2 should never be used as variables (except for
INI tags because noobs), but as 'expansion' and 'base' to make porting
to TS/FS more overseeable