Use same layout and interactivity for project members as group members and make code more consistent.

It's probably easiest to review the commits one by one, but keep in mind that later commits sometimes touch the same place as earlier ones, so look at the complete diff to add comments.

The project members page and group members page now look and work the same, with an inline "Add members" form, member search and editing of access levels and deleting without page refresh.

Before:

![Screen_Shot_2015-03-13_at_16.50.39](https://dev.gitlab.org/gitlab/gitlabhq/uploads/2cd023c48de0a643ce04df965f39e1f5/Screen_Shot_2015-03-13_at_16.50.39.png)

After:

![Screen_Shot_2015-03-13_at_16.50.02](https://dev.gitlab.org/gitlab/gitlabhq/uploads/fdef480daf2859ed74f5641af1f337b3/Screen_Shot_2015-03-13_at_16.50.02.png)

See merge request !1695