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
i still prefer the 2 (3) liner ;)

'''
file(STRINGS "${XBMCROOT}/version.txt" versions)
include(CMakeParseArguments)
cmake_parse_arguments(APP "" "VERSION_MAJOR;VERSION_MINOR" "" ${version})
'''