Revert "Do not import the VideoPlayer when running on Android"

This reverts commit 0848a86b325d27d8499778276a2305cd0e51019e.
Add an is_android() function that tests whether or not Tribler is running on Android
Use PIL instead of wx on Android to calculate the colourfulness
Use is_android() in GuiDBTuples and move vwxGui imports to the functions it is used in