- more cleanups:

- more cleanups:
- add pool argument to datamatcher_init
- add flags argument to repodata_search
- only add sentinal if SEARCH_SENTINEL is specified
- use kv.eof == 2 for sentinel like before
- rename dataiterator_match to dataiterator_match_obsolete
- add repodata_stringify function
- make datamatcher match simple strings so it can be reused
- add dataiterator_prepend_keyname to match keyname pathes
- rename dataiterator_jump_to_solvable to dataiterator_jump_to_solvid