Naming folder containing classes

CommonGameClassFiles
UtilityClassFiles
HelperClassFiles
MiscellaneousClassFiles
GameSupportingFiles

If certain class files tie these all together or wrapp them all up for a start up game to have a lot of higher level functionality simply right off the rip.

You can call it a Engine or FrameWork or even an Api though that usually denotes that it is a direct interface for or to low level calls.