GRP-06: Request membership in a group

Executive Summary: 
A community member (“requester”) needs to request to be added to the membership in an XSEDE group via a simple user interface.
User Importance Summary: 
XSEDE community members need to be able to define arbitrary groups of people to which they can refer throughout the XSEDE system for authorization and communication purposes.
Target Communities and Sizes: 
XSEDE users - 10,000 < N < 100,000