Reuse the same bib number for multiple conventions

[rdunlop]

In order to support the Italian Open Championships, we want to be able to reuse the same bib number multiple times through out a series of conventions.

In order to do this, the following will be added:

Permissions

1. Add the ability for a convention admin to be able to create a "Convention Series"
2. Add the ability for a convention admin to join a convention to a Convention Series as long as they are convention admin on all entries within that convention series
3. On the Convention Series page, allow displaying an overview of all registrants across all series, e.g. a table:

• Bib Number
• Convention A Name
• Convention A DOB
• Convention B Name
• Convention B DOB
• Convention C Name
• Convention C DOB
  And highlight any rows where the registrant's name or DOB is not the same.
  And show a link to the "Change bib number" page to allow the administrator to separate mis-associated entries.

Bib-Number reuse logic:

4. When a user is creating a registrant, recommend that they use registrants from conventions in the same series first, followed by conventions outside the series, in descending created_at order.
5. When a user creates a registrant from a previous registrant

• If the previous registrant is part of the same convention series, use that same bib number
• else search the user for a record in the same convention series with the same name/birthday, and use that same bib number
• else use the next available bib number within the convention series.

Bib-Number update logic

6. When using the "update bib number" feature, make it default to adjusting the bib number the registrant in all conventions in the series.
7. Allow the "update bib number" to affect only a single convention (in order to split/separate a registrant which may be co-joined with another by accident)