refactoring: move repo reading implementation out of dnf.Base.
refactoring: cleanup a couple of lint warnings in base.py.
conf: only 'main' is a reserved section name.

Also see 97daa7c3.
proxy username and password, for both CLI and API. (RhBug:1120583)
remove: conf.commands.

Not documented, not used.
transifex update
tests: refactor: rename test_resource_path() -> resource_path() and use it more.
Straighten up the exceptions when getting a packages header. (RhBug:1122900)

In the process, moves around the dnf.rpm methods to load the header.
Add Repo.updateinfo_fn.
Load UpdateInfo.xml during the sack preparation.
test: really don't break other tests with the DRPM fixture
test: support adding directory repos to Base stubs
test: add updateinfo to the testing repository
Add basic updateinfo command.
Add "updateinfo summary" command.
Add "updateinfo available" command.
Add "updateinfo list" command.
Add "updateinfo info" command.
Add "-v updateinfo info" command.
Add "updateinfo [<output>] installed" command.