Improve osbs specfile
Improve osbs specfile

- 'osbs' package now contains only binary and docs
- 'python-osbs' package introduced as counterpart of 'python3-osbs'
- %{_bindir}/osbs is now symlink to osbs2

jpopelka/osbs-client,vrutkovs/osbs-client,jpopelka/osbs-client,DBuildService/osbs-client,pbabinca/osbs,TomasTomecek/osbs,pombredanne/osbs-client,bfontecc007/osbs-client,projectatomic/osbs-client,pbabinca/osbs,DBuildService/osbs-client,vrutkovs/osbs-client,projectatomic/osbs-client,bfontecc007/osbs-client,twaugh/osbs-client,pombredanne/osbs-client,TomasTomecek/osbs,twaugh/osbs-client