Actually pass the response body to CommandListener implementations, per the interface contract.

Fixes #6878: TestSession>forward()>contentBeingForwarded always null in CommandListener.afterCommand().  Thanks  suayipozmen for the find and the fix.
Ignore exceptions during the clean-up process if failing to start a RemoteWebDriver instance.
The crowd has spoken and wants the original exception, not nested.
Fix #6770 setting a timeout when jetty has low resources to prevent hub from hanging.
Fix #6771 if a session times out and the browser was never started, it should still be cleaned up on the hub side.
BeforeRelease should then be a no-op and not throw.
Fix #6772 adding a configuration parameter to set the number of thread jetty uses.
Default = -1 = current behavior ( 255 thread from Jetty's default settings )
Fix #6773 consuming the request in all cases to properly release resources
the capabilities needs to be sent properly encoded.Capabilities for mobile for instance have copyright signs.