GRP-05: Invite members to a group

Executive Summary: 
A community member needs to invite one or more individuals (“invitees”) to become members of a group. The invitees will not become group members until they accept the invitation. The community member must have the administrator or manager role in the group.
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