LUN-718: added test for plugins template validation on site form.
LUN-718: added decorator for setting TEMPLATE_DEBUG on.
LUN-718: changed the way plugins in PLUGIN_TEMPLATE_REFERENCES
should behave. Raise errors when settings are not configred correctly.
LUN-718: Added tests for form validation on plugins templates.
+ Some code refactoring.
LUN-718: changed validation messages to include pages title.
Merge remote-tracking branch 'origin/master' into LUN-718

Fixed conflicts:
	cms_templates/admin.py
	settings_test.py
LUN-718: changed validation messsages.
Fixed the way PLUGIN_TEMPLATE_REFERENCES setting is loaded.
Renamed some vars and functions for code readability.
LUN-718: changed variable names to be more explicit.
Merge pull request #18 from pbs/LUN-718

Lun 718: changed validation messages