Consolidate admin / user setting pages for projects and groups

Description

Admin users have separate pages for every project and group, yet can only access a small part of the settings of the projects and groups there.

Proposal

We consolidate the two into a single view with a clear 'admin' part and the rest of the interface.
Get rid of Admin Area group-specific settings admin/group/group, and forward to the group settings instead via "Edit".

Further details

• remove admin/group/edit and admin/group/new pages because it duplicates group/new and group/edit.
• link new/edit group from admin area to regular UI
• if admin/group/edit has settings not available in regular UI -> move it there.
• UX: make sure its obvious that new/edit links for project and groups in admin area will take you to regular UI (outside of admin area)

Links / references