API GridState_Data values can have default values specified during retrieval.
Fixes issues with GridStata_Data being returned from various states when value types are necessary.
Pruning of dead code from GridFieldAddExistingAutocompleter
Documentation for GridState
Merge pull request #2522 from tractorcow/pulls/3.2-gridstate-api-fix

API GridState_Data values can have default values specified during retrieval.