Added missing implementation for a few functions.

I added GetDataFilePath which is based on FHS. You can use OBS_DATA_PATH to override the hardcoded values.
I also added an implementation for GetMonitors which uses XCB, not Xlib.
I tested the "make install" process to make sure the file layout was correct in ${prefix}/share.
The appropriate changes to make the above possible were made accordingly in the autoconf files.