Project members UI

## What does this MR do?

New UI for project members that includes groups.

## Screenshots (if relevant)


### Project members

![Screen_Shot_2016-09-02_at_15.13.27](/uploads/b9d4a634d44b7b7bbb6eddb10aee86bd/Screen_Shot_2016-09-02_at_15.13.27.png)

### Group members

![Screen_Shot_2016-09-02_at_15.13.36](/uploads/c15c173e68b2c0b49bcd06ca560269d3/Screen_Shot_2016-09-02_at_15.13.36.png)

## What are the relevant issue numbers?

Part of #19868 

Closes #21320 

See merge request !6148