docs/source/conf.py: Make sphinx display __init__ method docstrings

We had to set the autoclass_content param in conf.py.

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
avocado: Fix class docstrings

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
avocado.plugins.xunit: More docstrings

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
avocado: More docstring fixes

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
Merge pull request #47 from avocado-framework/display-init-docs

Display init docs