Added parsing ClientTransportPlugin lines with multiple transports provided by one pluggable transport

This commit fixes the TODO about parsing ClientTransportPlugin lines like 
`obfs3,dummy,b64 obfsproxy managed`

It adds a new dictionary to map between the individual transports to the combined transports name. This will be useful for the launching_multiple_chains commit as it can check if a combined transport has been launched and not launch any new transports.

Eg. `obfs3,dummy,b64 obfsproxy managed` will be launched for the first pt in a chain. If the chain is `obfs3|b64`, then obfs3 will launch first and register a transport under the full combined name `obfs3,dummy,b64`. When b64 attempts to launch it will check if the full combined name has already been launched and not launch another obfsproxy.