Tasks admin tags - WIP


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

Still Pending:
Control params for new action "reorganize" in tags_controller 
Adding control to avoid merges without new names.
Adding warning popup before merging or deletion
Adding Tests
'selected' no es parte de este concepto, este método recibe unos tags simplemente, no unos 'selected tags'.

    def rename_tags(new_tag, old_tags)