Fixed ERRAI-646: Destroying beans that have observers no longer causes unconditional CDI remote unsubscribe messages

We now first check if other matching local observers are present before unsubscribing from remote events of that type and qualifiers.
Upgraded to MVEL 2.1.6.Final
Additional fix for ERRAI-646: Avoid resetting SSE channel every 60 seconds

- For SSE, we now send an empty JSON array as data every 45 seconds to avoid inactivity timeouts
- SSE support was removed from StandardAsyncServlet
Upgraded to MVEL 2.1.7.Final
Removed comment to deprecate FROM_UI because it turned out to be useful (see ERRAI-643)
Removed quickstart docs (no longer used)
Updated to version 2.4.1.Final
Updated to new version 2.4.2-SNAPSHOT
Fixed RPC error reporting so it displays the additionalDetails sent from the server

This was a surprisingly deep-cutting change: RPC error handling used to go through 3
times as many callbacks as it does now (and it ended up displaying a useless client-
side stack trace in the error dialog)

I also eliminated the transportToBusCallback in favour of a new public sendLocal()
method that does what it says. Transports now deliver messages into the bus itself,
which simplifies all message deliveries--not just errors.