dnf.cli.commands.err_mini_usage() changed name.

see also DNF commit b490558. This is why no plugins should use non-API calls.
build: simplify plugins/CMakeLists.txt.
tests: add __init__.py to make tests a module and use abs imports
Add a special ArgumentParser to parsing plugin cmd arguments and options

This makes it possible to add private command line option to a plugin there is
adding new command to dnf and also make it possible to define what arguments
is required and show the user if the wrong options/arguments is given.
download: update the download plugin with --source, --destdir & --resolve options

--source will download the source rpms.
--destdir set where the downloaded files are placed.
--resolve download uninstalled dependencies also.
build: install the download plugin
debuginfo-install: fix logger debug messages

When we trying to install debuginfo rpms I want to log all enabling
repos, but there typo. format(id) should be format(di).
[cutted]
enabling <built-in function id>
enabling <built-in function id>
enabling <built-in function id>
enabling <built-in function id>
enabling <built-in function id>
enabling <built-in function id>
enabling <built-in function id>
enabling <built-in function id>
enabling <built-in function id>

Signed-off-by: Igor Gnatenko <i.gnatenko.brain@gmail.com>
debuginfo-install: fix description

Signed-off-by: Igor Gnatenko <i.gnatenko.brain@gmail.com>
debuginfo-install: doesn't install latest pkgs (RhBug: 1096507)

This is caused because I've installed 'p' (current provider), but we
need to install 'pkg', which correctly throw installed and available
packages.

Reference: https://bugzilla.redhat.com/show_bug.cgi?id=1096507
py3: absolute imports and unicode literals everywhere.

Avoids surprises later.
copr: honor -y and --assumeno
copr: remove repofile if failed to enable repo

If we trying to enable repo - it trying to download and creating
repofile, but when it's failed (generally Copr repo doesn't exist) -
it's not deleting this repofile.
doc: add documentation and man pages
doc: cleanups, form, style.
doc: cosmetic: project name in the documentation.
doc: put each synopsis on new line
tests: stray print() in test_download.py.
doc: packaging: add license block to each .rst.
build: add sphinx to build requires.
build: 0.0.8-1