Additional filters and sections for admin pages

[dboyer]

A few additions requested for admin pages:

• On a club's admin page (i.e. /admin/clubs/101#/), add a section that shows the club ambassadors for that club and links to their profile
• On the club ambassador data grid (/admin/club_ambassadors), add a "has a mentor profile" filter similar to the one that is on the ChA page
• On the chapters admin page (/admin/chapters), add a country filter
• On the participants page (/admin/participants#/), add an option to filter for participants who are not in a club or chapter - perhaps a yes/no option similar to onboarded