Fixed bug that caused intermittent failures in EventObserverIntegrationTest

The problem was that we relied on a runtime check (canMarshall) to decided whether or not to advertise a CDI event type to the server. However, this check will always fail for abstract types as canMarshall will return false. So whenever the bus reconnected we failed to advertise observable interfaces and abstract types to the server. Since we already collect all local-only event types on startup this check can now be removed.
Change forge-errai link to v2.0.0.Beta1 tag.
Set width of getting started screenshots to 650.
Lots of doc improvements.

Linked to Errai Forge Addon tag (Beta1).
Add plugin tips and general editting up to Marshalling section.
More doc improvments.

Add plugin tips and manual setup notes up to errai navigation.
Move all setup/configuration instructions in those sections to single
location.
Finish restructuring of docs up to Configuration section.
Reorganize Configuration section of docs.
Commit change to docbook reference.xml
added support for remote call interceptors without the need to annotate the remote interface (works for Rpc and Jax-rs).
Only run validator generator when needed (it triggers heavy reflection scanning)
Merge branch 'errai-interceptors' of github.com:EricWittmann/errai
Adding boolean property to skip subtype checking for reloadable types (perf. improvement)
Only scan JARs with ErraiApp.properties for LESS files
Moving simple.less file to be picked up by MetaDataScanner
modified rpc and jax-rs interceptor chain processing to be async.  added IOC support for interceptors (now if the interceptor is a managed bean it will be looked up via the bean manager rather than simply created new each time
Progress on ERRAI-688: Introduced ClientSyncWorker
Progress on ERRAI-688: Introduced Sync/SyncParam annotations and prepared test
Moved MockClientSyncManager to separate file and black listed it
Added explanations about blacklisted bean
Progress on ERRAI-688: Begun implementing codegen required for @Sync