Make more tablet apis available in the preferences to pick from

I´d love some option to customize which pen/touch api to use.
Might only be useful in some fringe cases, like using a convertible laptop or some older tablet, but a lot of tools like zbrush or blender allow you to pick your preferred tabled api.

Justification

Its just another layer that allows users like me to customize Instamat to your need.
People that do manual texturing in particular often have specific needs due to hardware restrictions etc.

Implementation Details

There are several tablet apis that should be choosable in the preferences:
Windows ink, wintab and maybe wmevent (the latter I only know from Zbrush).