Geokey

Improved serializer for categories and fields, now including "is_displayfield" - to determine whether the field is set as a display field for the category.

Fixed base settings, now including "static" as a main dir for static files.

Fixed installing correct version of Django alongside the GeoKey - latest version between version 1.8 and 1.10 (excluding the 1.10 alpha and future releases for now).

Fixed local settings, now including main static dir when running "collectstatic" from GeoKey installed via PyPI.

Fixed removing user from a user group.

Improvements
- Each category now has ability to set an expiry field, that is used by contributions to set the date (and time) when it should be not available to the public anymore. An expiry field can always be changed or removed as a setting - none of the data is deleted.
- Public API endpoint for getting GeoKey information now includes all extensions added, even those that are installed for use by superusers only. This allows front-ends to decide what functionality can be used if it relies on some extensions.