avocado.job: If possible, write an HTML report at the job results dir

If the HTML plugin is enabled on this install, write a
report at html/ on that job results directory. This will
help people to read avocado test results on a portable
and pleasant way.

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
setup.py: Add plugin resource files

Package plugin resource files, as they're necessary to
the given plugin's functionality. Update MANIFEST.in
with the new data dir.

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>
avocado.spec: Add subpackage plugins-output-html

Add a subpackage plugins-output-html, that will turn
HTML functionality optional in avocado. This way
we don't force people to install unnecessary dependencies
for the functionality they actually want.

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