Move default location of collected static files and uploaded media files

Put them in the `wsgi` folder. This will reduce the number of folders in the
project root and will match location of the `static` folder in OpenShift
Set STATICFILES_DIRS and TEMPLATE_DIRS

Explicitly add `venelin/static/ to STATICFILES_DIRS and 'venelin/templates`
to TEMPLATE_DIRS. Theese directories will have higher priority then all
other apps for looking for static files and templates.
Remove deprecated ADMIN_MEDIA_PREFIX from settings
Put django_extensions to INSTALLED_APPS

django-extensions is in requirements.txt and in setup.py there is no need
to try to import it and then put it in INSTALLED_APPS. It will be always there.