Start application GUI

[idmadj]

This change adds the GUI logic needed to map buttons to programs/applications.

[thomasaull]

Is this going to to add the possibility to use different button settings on a per application basis? Would be awesome :)

[idmadj]

@thomasaull This allows starting an application by pressing one of the tablet's button. For instance pressing button 1 to launch OneNote.

#585 Might be a good starting point to implement the feature you're thinking of. AFAIK nothing has been done yet to detect which application has focus.

[thomasaull]

Thanks for the pointer @idmadj I'll check it out :)