2. Update COMPREHNSIVE_THEME_DIR to COMPREHENSIVE_THEME_DIRS
3. Update paver commands to support multi theme dirs
4. Updating template loaders
5. Add ENABLE_COMPREHENSIVE_THEMING flag to enable or disable theming via settings
6. Update tests
7. Add backward compatibility for COMPREHEHNSIVE_THEME_DIR

Resolves conflicts between reverts of pattern library test pages and multi-site comprehensive theming, and the re-introduction of pattern library test pages. Fixes a pipeline rendering test which relied on other tests updating assets. The test now ensures that static assets are available before running.

This reverts commit a796b563.

Conflicts:
	lms/envs/common.py
	openedx/core/djangoapps/theming/models.py
	pavelib/assets.py
	pavelib/paver_tests/test_assets.py

FEDX-93

These are developer only pages, so can not be seen in production
environment. On devstack, you can access these pages in LMS and
Studio at:

    /template/ux/reference/pattern-library-test.html

This is the second attempt to enable the Pattern Library. The
first attempt broke Django Templates and didn't work correctly
with right-to-left styling.

This reverts commit 845e3708.

This reverts commit 845e3708.

FEDX-93

These are developer only pages, so can not be seen in production
environment. On devstack, you can access these pages in LMS and
Studio at:

    /template/ux/reference/pattern-library-test.html

- Update to latest version of watchdog.
- inotify doesn't work on nfs share in devstack. Use polling instead.
- Some editors (vim) do not trigger modify events in their default
  configuration. Rebuild assets on all filesystem changes, and debounce
  when changes happen too quickly.

ziafazal: improvements need for multi-tenancy
ziafazal: fixed broken tests
ziafazal: no need to add setting in test.py
ziafazal: added hostname validation
ziafazal: changes after feedback from mattdrayer
ziafazal: fixed branding and microsite broken tests
ziafazal: make STATICFILES_DIRS to list
ziafazal: added theme directory to mako lookup for tests
ziafazal: added more protection in test_util
saleem-latif: Enable SCSS Overrides for Comprehensive Theming
saleem-latif: Incoporate feedback changes, Correct test failures, add tests and enable theming for django templates
saleem-latif: Correct errors in python tests
mattdrayer: Fix invalid release reference
mattdrayer: Update django-wiki reference to latest release
saleem-latif: Update Theme storages to work with Caching, Pipeline and collectstatic
saleem-latif: Incorporate feedback changes
mattdrayer: Pylint violation fix
mattdrayer: Fix broken pavelib test

This reverts commit 954dae58.

ziafazal: improvements need for multi-tenancy
ziafazal: fixed broken tests
ziafazal: no need to add setting in test.py
ziafazal: added hostname validation
ziafazal: changes after feedback from mattdrayer
ziafazal: fixed branding and microsite broken tests
ziafazal: make STATICFILES_DIRS to list
ziafazal: added theme directory to mako lookup for tests
ziafazal: added more protection in test_util
saleem-latif: Enable SCSS Overrides for Comprehensive Theming
saleem-latif: Incoporate feedback changes, Correct test failures, add tests and enable theming for django templates
saleem-latif: Correct errors in python tests
mattdrayer: Fix invalid release reference
mattdrayer: Update django-wiki reference to latest release