nevra.h: added hy_nevra_to_query function
nevra.h: added hy_nevra_evr_cmp function
subject: added types
subject: added create, free functions
subject: added possibilities reldep
subject: added possibilities nevra
subject: added possibilities nevra real
subject: refactored python nevra possibilities
subject: refactored python reldep possibilities
subject: removed unneeded functions