Unregister RPC callback objects
Unregister RPC callback objects

Call unregisterCallbackObject for RPC objects in removeWebinosEventListener
and dispatchWebinosEvent when they aren't used anymore. Also add some type
checks for params for these methods and raise new WebinosEventException if
they type check fails.

Jira-issue: WP-405

hansmy/Webinos-Platform,webinos/Webinos-Platform,webinos/Webinos-Platform,webinos/Webinos-Platform,hansmy/Webinos-Platform,krishnabangalore/Webinos-Platform,webinos/Webinos-Platform,webinos/Webinos-Platform,webinos/Webinos-Platform,krishnabangalore/Webinos-Platform,webinos/Webinos-Platform,hansmy/Webinos-Platform,webinos/Webinos-Platform,hansmy/Webinos-Platform,hansmy/Webinos-Platform,krishnabangalore/Webinos-Platform,webinos/Webinos-Platform,krishnabangalore/Webinos-Platform,krishnabangalore/Webinos-Platform,krishnabangalore/Webinos-Platform,hansmy/Webinos-Platform,krishnabangalore/Webinos-Platform,krishnabangalore/Webinos-Platform,krishnabangalore/Webinos-Platform,hansmy/Webinos-Platform,hansmy/Webinos-Platform,hansmy/Webinos-Platform