split repo_find_pubkeys from repo_verify_sigdata
rename repo_find_pubkeys to repo_find_all_pubkeys, add repo_find_pubkey
tweak findproblemrule heuristic for conflicts

Return conflict instead of requires if one of the required package
conflicts with an installed package.
port to python3
fix Chksum.add() method also for perl/ruby
tweak python version detection, add Datamatch.binary()

Also no longer misuse swig's cdata typemap.
support DELTA_LOCATION_BASE for completeness...
pysolv: more python3 adaptions