Community cv

For a better overview on the current changes towards a Community curated CV, @abbrent , @alhajtah , @extbrinc .

To dos (for now):

• ? change naming of original entries more explicit, (e.g. ActionTypeCommunity.original_id instead of ActionTypeCommunity.action_type_id). Otherwise it is hard to distinguish from the other foreign keys (e.g. ActionCategoryCommunity.action_category_id, its easier for OOP and filtering - ?
• Delete MeasuredQuantityUnit since besides default_limit_min and default_limit_max its only a link table
• add fixtures for default entries
• ? besides filter for community (e.g. /api/v1/actioncategoriescommunities/?filter[community.term]=GFZ_Hydrology) also filter for original entry (e.g. /api/v1/actioncategoriescommunities/?filter[original.term]=Platform)?
• adjust admin interface
  • add missing community Admin pages
  • pre filtered selections. Otherwise nonsense combinations (e.g. in Action Types Communities: Action Category (original) = "configuration" and Action Type (Community) = "Device Observation" for community == default)