OB-94: using TEMPLATE_ROOT config variable.
OB-94: OBJAVI_URL is a settings variable.
OB-138: Moved static files to the objavi app folder.

This removes the need to specify the location of static files using the
STATICFILES_DIRS setting, which in turn removes the need for the
OBJAVI_SOURCE_DIR settings.
OB-138: Use MEDIA_ROOT for data files.

This will also allow usage of Django file storage access functions.
OB-138: Removed settings for which default values are adequate.
OB-139: Moved the templates directory to objavi module.
OB-140: Removed the lulu module.
OB-140: Removed twiki interface.
OB-140: Removed obsolete setup script.
OB-140: Removed wikibooks2epub.