cleanup and minor fixes

cleanup configure, fix xbmc-addon-bindings version parsing and make addons build on linux with cmake.
PREFIX stuff is not touched here.
@Montellese ping
We could allow setting APP_VERSION_MAJOR and APP_VERSION_MINOR through -D arguments to the cmake executable (in case we ever want to be able to build the addons completely outside of xbmc tree) so maybe change the message to
```
Could not determine app version! Make sure that APP_VERSION_MAJOR and APP_VERSION_MINOR are defined!
```