INT-3103 TCP Propagate Exceptions to GW Thread

Previously, when a calling thread was waiting for a reply, and an exception
occurred on the socket, the exception was not propagated to the thread and
it would eventually get a timeout, but with no indication of the problem.

Propagate the exception to the calling thread by invoking onMessage()
with an ErrorMessage.

Ignore the ErrorMessage in other TcpListeners (inbound adapter, gateway).

Ensure NIO closes are not missed by sending an ErrorMessage when the selector
thread detects a closed channel.

Add tests for Net, NIO, cached and failover connection factories.

Polishing

Remove left-over debug logs; add comment to setReply().

Add comments for ErrorMessages in onMessage().
INT-3054 URI Variable Mapping Improvements

Permit missing URI vars in HTTP outbound gateway

Do not attempt to evaluate uri variables that are not in the URL

The http gateway might not know what uri variables it might obtain in the URI.
This patch makes sure that only the uri variables defined in the uri are parsed (the rest are ignored)
INT-3054: Add ExpressionEvalMap Support

Use an immutable Map wrapper to evaluate expressions
only when accessed.

Polishing
Merge pull request #822 from wwadge/INT-3054

* INT-3054:
  INT-3054: Add ExpressionEvalMap Support
  INT-3054 URI Variable Mapping Improvements