avocado.core.data_dir: Fix docstring

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
avocado: Simplify setting test default values

Instead of using self.params.set_default() manually for
each default value, allow test writers to set a
default_params attribute with default params, and
set them at test class init time. This way we keep
things even shorter, while allowing avocado tests
to be used stand alone.

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
docs: Update documentation with multiplex config docs

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
avocado.linux.software_manager: Fix bug found by pylint checker
Reorganize unittests and functional tests

In order for people to run all avocado tests at once,
move and reorganize tests under a directory called
selftests. For someone to run all self tests in
avocado, one would have to execute:

    selftests/run selftests/all

This is a shortcut for developers. .travis.yml
was also updated to run tests based on the new
directory structure.

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>