avocado.test: Use unique_id to build temporary path.

if job.unique_id is available in test, use this information
to build the temporary path used in attribute workdir.

The template format is $TMP/job-<unique_id>-<random>/.

Signed-off-by: Ruda Moura <rmoura@redhat.com>
Merge pull request #167 from ruda/test_temporary_dir

avocado.test: Use job.unique_id to build temporary path.
avocado.docs: Update documentation regarding argument parsing.

Update documentation regarding the last update on argument parsing.
Like option --silent goes to run subcommand and there's no
need to quote for multiples test names.

Signed-off-by: Ruda Moura <rmoura@redhat.com>
Merge pull request #170 from ruda/argument_parse_docs

avocado.docs: Update documentation regarding argument parsing.