* ice: Added functions to get selected candidates.
Also added a function to get the type of a candidate. This can be used when
sending data to handle relay candidates, where data must be sent through the
TURN client.
* Forward-declare "ice_cand" before it is used.
* ice: export enum ice_candpair_state
this is related to the work of merging 2 ice-stacks into 1:
https://github.com/creytiv/re/wiki/ICE-Stacks-merge
* ice: remove ice session (struct ice)
* ice: remove list, cleanup
* ice: use local role instead of offerer
