Generate the class given in class if not explicitly given

[redstrate]

This is still a part of the API, and thus have required even new .tablet files to fill this out even though it's superseded by IntegratedIn. So let's generate them programmatically.

This turns devices that are IntegratedIn=Display to the Cintiq class, IntegratedIn=Display;System into the ISDV4 class, and everything else into the Bamboo class.

(This definitely needs more test cases)