[PERF-303] Integer XBlocks/XModules into the static asset pipeline.

This PR, based on hackathon work from Christina/Andy, implements a way to discover all installed XBlocks and XModules and to enumerate their public assets, then pulling them in during the collectstatic phase and hashing them.  In turn, the methods for generating URLs to resources will then returned the hashed name for assets, allowing them to be served from nginx/CDNs, and cached heavily.

This reverts commit a796b563.

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

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

TNL-3137

TNL-3137

TNL-3137

TNL-2487