Revert "Force eager startup of DispatcherServlet"

This reverts commit c0a951e6d82a418caec40abdd6639e2f1e44b404.
XD-361 Create trigger shell command
Added triggers link to admin controller
Added TriggerTemplate to implement the TriggerOperations for SpringXDTemplate
Added "trigger create" trigger shell command with options

Fix ReferenceDoc to include Trigger command title
Streamline exception hierarchy. Make sure they propagate to client properly
Got rid of leaf exceptions
Factor out common bean defs.