api: groups: add comps.Package, add group.package_iter(). (RhBug:1079932)
cosmetic: move stuff around in comps.

alphabetical ordering of same-level classes.
api: explain that Base is a context manager with a close().
tests: fix terminfo capability independence.
tests: refactor: make Term tests more isolated.
refactor: move install, downgrade and upgrade commands into separate modules.
tests: fix tests broken under foreign locale after 32818b2.
api: add Base.package_install et al. and Base.add_remote_rpm(). (RhBug:1079519)

Make the CLI use these building blocks.

Document the new API calls.
repo: Repo.cachedir is not a list.

And librepo does not like inflicting a non-list on Handle.urls. In fact,
Python displays deprecation warnings with -Wall.
fix PendingDepreaction warning from rpm in _getsysver().
fix: leak: couple of files objects left open.

Found with -Wall.
fix: resource leak in yum.misc.checksum() under py3.
fixed local downgrade error
fixed wrong named variable
fixed py3 error thrown by search command