started android pause system
Started implementing better FileManager on android
Added ability to select specific texUnit when binding and unbinding textures
Added Resource baseclass
Unfinished work on adding  Resource baseclass, and functions to ResourceManager
Fixed particle bugs
Creating directories and files now works properly on android.

Fixed/implemented everything so that it works on android. Windows filemanager still needs to be changed.
Also now always opens the files as read/write
Cleaned header and changed GetFileSize to return the current file size
Fixed windows implementation of FileManager
Merge branch 'feature/FileManager_overhaul' into develop
unified resources, added override checks
added static lists of needed objects for context recreation
implemented resource manager functions
added focuscallback to window creation
fixed testscene
Added missing implementation to RigidBody
Something done
Work on branch
Added customizable callback for Android's "Back"-button
Actually set the default color