Minor non-functional changes
Rename rcn_common.h -> rcn_node.h to match internal class name RCN_Node
Add RCN_Host class which abstracts away channel admininstration on the host side of the RCN network
Consistent naming
Make sure update_filter is not invoked with uninitialized old_level
Add RCN_Controller, RCN_Node counterpart for RCN controller nodes