Docs: Separate subtest section

*  Moved everything except the examples into
   a separate ``subtests.rst`` file.
*  Updated the content of the subtests section
   including adding more details about the
   sub-subtest mechanism.

Signed-off-by: Chris Evich <cevich@redhat.com>
Docs: Update example docstrings to new standard format

Signed-off-by: Chris Evich <cevich@redhat.com>
Docs: Merge old subtest docs into docstrings w/ new format

Contents of ``subtests.rst`` were moved/merged into the
main module docstrings for each subtest.  Examples
were updated to reflect docstring format.

Signed-off-by: Chris Evich <cevich@redhat.com>
Docs: Minor fixes, include version/revision

*  Fix release value to represent version less revision number.
*  Add substitutions for version & revision in Title and API section.
*  Fix prerequisites link.
*  Prepare subtests section for inclusion by external file.

Signed-off-by: Chris Evich <cevich@redhat.com>
Docker: Add run_checkdocs.py, call from travis

This patch adds `run_checkdocs.py` helper, which checks all
existing files and it's documentation. This check is added in .travis.yml
and will be executed with each test.

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>
Docker: Auto-generate subtest docs

Moved generic subtest locating / naming code from run_checkdocs.py
into class dockertest.environment.SubtestDocs.  This module by
has no dockertest-dependencies, so it's safe to call from stand-alone
scripts.  Added methods for extracing docstrings from subtest modules
and joining them together.  Added unittests to verify all functionality.

Updated Makefile to properly identify changed subtest modules so
subtest documentation will be rebuilt automatically.  Updated
index.rst to include subtests.rst file.  Added subtests.rst as
a dependency to all targets.

Modified travis.yml to build documentation prior to running
documentation checks.  Modified run_checkdocs.py to point
at subtests.rst instead of index.rst.

Signed-off-by: Chris Evich <cevich@redhat.com>
Merge branch 'subtest_docs' of https://github.com/cevich/autotest-docker into doc_checker