Addition to ERRAI-740: Servlet that provides user agent specific manifests
Make sure linkers don't cause deployment issues in dev mode
Fix RPC interceptor chaining bug with async interceptor creation.
Use RestClient domain and path when setting cookies for JAX-RS CookieParam.
Update GWT to version 2.6.1.

Some expected test-behaviour in errai-jaxrs and errai-data-binding needed to be changed.
The guava version was also upgraded to avoid gwt compilation errors in errai-navigation.
Added docs for offline mode
Serve an empty manifest in dev mode
Ensure timers are always cancelled in bus tests
Make sure offline linker works for both GWT 2.5 and 2.6
Increase MaxPermSize in for errai-forge-addon tests.
Don't put split points (deferredjs files), junit and hosted.html into offline manifest
Fixed/Introduced backoff logic for SSE