Revise Enhanced User Groups proposal

Replaces the "job modification permissions" proposal with
a simpler concept of "submission delegates" that are able
to submit jobs on behalf of a group, and retain the ability
to modify those jobs, but can't modify that group's other jobs

Also nominates a release time frame for 1.0

Change-Id: I95bc9a6ab11538aa37390c5ed2d127c16ece9b3b