Add group selector to table embed in football admin

Allows embed of goupr tables for tournaments (e.g. the World Cup).
Add groupt tables to the football admin

Table embeds can be be selected for specific groups. It is also
possible to create a snap for a group table from the Fronts section of
the football admin.
Add missing template file
Merge pull request #4272 from guardian/football-admin-group-tables

Add group tables to the football admin