Admin tags tasks

This is a WIP PR to allow code review in parallel

- Refactored code to avoid extra code in _grouped_index.html.haml including test to verify
- Added main logic and bootstrap style (based on checkboxes) to allow merging and deleting tags if user is admin
- Removed unused flags resources
- Added some styles to allow showing debug information in screen while running in dev environment

Pending:

- Adding control to avoid merges without new names.
- Adding warning popup before merging or deletion 
- Adding Tests
Use 2 (not 3) spaces for indentation.