Combined member/group settings page improvements

With the recent change that combines the member and group settings pages, there are a number of UX improvements that can be made.

Current UI:

We should simplify sharing groups and remove redundancy of deleting shared groups. We should also look at the ux that is involved with adding or updating a member that is a part of a project. It is strange that you can select current members in this dropdown and the button still says "Add to project" even when they are already in the project.