Add ability to remove (empty) partner groups

[cielf]

Summary

Add ability to remove empty partner groups

Why?

As a bank's business evolves, they may end up using different partner groups, and want to remove the old ones for adminstrative simplicity.

Details

Where this needs to be put

Login as org_admin1@example.com. Select Partner Agencies, then All Partners, and the Partner Groups tab.
Iff the partner group has no members, add a "Delete" button under actions.
Pressing delete will cause a confirmation "Are you sure (cannot be undone)?" to appear. On selecting yes, the partner group will be deleted.

Criteria for completion

• behaviour as above
• automated tests to support that behaviour

[Aaryanpal]

@cielf Please Assign this

[cielf]

You've got it.

[Aaryanpal]

Done @cielf