Build "Group" receptor use case

[zippy]

Group features:

• send a message to the group channel
• listen to a groups channel
• find channels

The purpose of this is to get multiple ceptr shell nodes talking. this will make us create ceptr-network scaffolding (including identy), and synchronization in the accumulator.

[zippy]

as of ca6f6e61abe9 we the most naive implementation of a group protocol works. This protocol assumes 2 roles: group, member, and has 2 interations: enrollment, and converse. The first a member uses to enroll in a group, the second, an member uses to send a message to a group, which then simply gets relayed to all group members.