Combine/link and evaluate Stands submissions

[rishabhptr]

In certain cases we want to combine two or more stand/booth requests together so that we can accept them for a single table/stand.

The user would submit independent requests and we may be able to link them together to a single table.

The Approach could be as:

1. Create a new model for combined booth request which would have a has_many relationship with booth model.
2. Admin/Organizer would visit booth/index.
3. The will be two tabs, the first one will be the default and the second one for the combined requests.
4. User will be able to click on second tab to see and update all the combined groups or create a new group by selecting a given number of stands.
5. These combined booths now will have a single state machine, and when accepted will only consume 1 entry from the booth_limit.