Use rid (CyCoreSystems#86)

* add resource ID tool

* use rid-based IDs

handle Marshal/Unmarshal of channel variables

Add support for ChannelVars on ChannelData

Fixes ari-proxy#18

revert last commit; stupid

ext/record: failure to delete during save is not an error

ext/play: fix MatchNone

ext/play: add MatchNone

fix ChannelContextOptionFunc type definition

add channel context helper

bridgemon: load initial bridge data before returning