service rm command to remove local (and published) services

[ryankurte]

Services should be removable from local tracking (and, the network).
Local removal:

• Add Remove command to rpc
• Update client
• Add rpc::service::Remove handler to daemon

Network object removal:

• Add Delete message to core
• Add Delete message handling to daemon network message handling
  • Validate remove message signed with service key
  • Forward remove message to nearby peers
  • Purge entries from database
• Send Delete message on rpc::service::Remove command