Removed compile-time dependency from errai-ui to errai-cdi-client

Fixes https://issues.jboss.org/browse/ERRAI-658
Removed ScopeUtil to get rid of a dependency to weld internals

- Its purpose is unclear to us: The tests and demos don't seem to be affected by removing it
- The theory is that the async dispatcher (which is no longer used with errai-cdi) necessitated associating the servlet request with Weld's request context because it separated the incoming request thread from the actual worker thread
Merge branch 'ERRAI-658' of github.com:jbarop/errai