* INCR-194
* fixed error, the import absolute_import instruction should have been at the beginning of the file
* added empty line required by PEP 8
* fixed comments order
* trailing whitespace fixed
all dirs must now go into COMPREHENSIVE_THEME_DIRS.
Move comprehensive theming setup section out of startup.py and into
settings files using new 'derived' functionality.
Add 'derive_settings' at the end of all top-level Django settings files.
Move validation of comprehensive theming settings into new apps.py
theming file.
Split theming code into code safe to run before settings are initialized
-and- after settings are initialized.
The system checks require database access, which is not available when building Docker images. This relaxes the check, allowing the command to execute without a database.
ECOM-6634
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
