check_package*: support overriding osc API

This happens via -A on the osc level and via --api on the
check_package* level.
check_package*: allow prepending to REPO

This is usefull when building in abother BS and want to prepend
strings like "openSUSE.org:".
kde: add 4.12 packages
Merge pull request #30 from jirislaby/master

kde 4.12