ComptonConfiguration: switched to libconfig as a configuration backend.

To make this possible, a dirty vapi binding has been written (it ships in vapis/).
It contains only the methods that are useful for us now, and it's pretty bad written.
libconfig.vapi: set_* methods return only a status boolean.
compton: added write support.

Whenever a setting is changed in dconf, it will immediately syncronized in the
compton configuration file.
compton: added initial compton.conf set-up from the dconf schema's default values.
schemas: change default configuration-file path to ~/.config/vera/compton.conf.
compton: added compton autostart, with support for on-the-fly activation/deactivation.
0.25
Updated .gitignore
Merge branch 'master' into debian
0.25-1