Undertow: lots of code movement but only a couple of functional changes

The functional changes were:
1) Offload blocking requests to worker threads using exchange.dispatch
2) Use default numbers for IO/worker threads

The rest of this commit is just shifting code around.  Individual handlers
went into their own classes.
Update Undertow version

Gives a slight speed boost due to path handler improvements
Don't use snapshot netty version

This at least allows the test to run. This is not the most
recent version of netty as it appears the API changed between CR and final.