Bugs: BLZ-287 - Potential null pointer in MessageAgent set destination method.
LCDS-522 - Add more configurable reconnect handling for connecting up again over the same channel when there is a connection failure/outage.
Checkintests Passes: Yes
* MessageAgent (conceptually an abstract class but that's not supported by ActionScript) now defines a default value for the agentType member used in logging output - fixes BLZ-287.
* ChannelSet now resets to the beginning on its channels upon manual disconnects or otherwise. This fixes the scenario of starting off on streaming or RTMP, loosing connectivity temporarily and then getting stuck on a fallback polling channel. Chances of reconnecting on the preferred channel are better now, and manual disconnects/reconnects if you end up on a fallback channel that you don't want to stick with are now possible.
* Also, updates to Channel to support LCDS-522, and longer-duration reliable messaging reconnects.