Add options for 'location' attribute input
Add support for multi-value attributes and refactoring posts save

* Adds cardinality column to attributes
* Refactor posts api to avoid double handling all values when saving
* Handle multi-values in API
* Add special handling for complex (ie Point) values
* Validate cardinality limit (ie. make sure # of values are within limit)
Make posts api return multi value fields properly and add tests

* Also adds Link attribute type used in test
Merge branch 'posts-improvements-for-migration' into migration-script
Import news media items into posts 'news' field
Fix location import from sql
Import video media into posts
Fix location checks to make sure 0,0 locations still get saved.