Docs:  Content and build updates

*  Updated documentation content
*  Fixed problem of double-building subtests.rst and defaults.rst
*  Fixed missing TOC in subtests.rst

Signed-off-by: Chris Evich <cevich@redhat.com>
dockertest: Split documentation module

The documentation module was becomming large and
unweildy at 1000+ lines.  Moved all low-level dependencies
into ``docdeps`` module. Adjusted unittests accordingly.

Signed-off-by: Chris Evich <cevich@redhat.com>
pylint: Fix 'too few pub methods' problems.

Most are simply disabled since the designs are based
on builtins or there's a good reason for not changing.

Signed-off-by: Chris Evich <cevich@redhat.com>
Merge pull request #425 from cevich/docs_update

Docs update