Move Pointer class
Implement Subset Groups
Subset Group Style overriding logic
Pull up property
New M/V implementation of Data Collection View
Make DataCollectionModel read-only, but auto-synced with underlying Data
Integrate DataCollectionModel into gui. UNFINISHED
Update LayerTreeWidget and EditSubsetMode for SubsetGroups.
UI tweaks to handle SubsetGroups gracefully
Tweak how style changes behave and are presented in UI
Remove old data_collection_view