First functional version of sharednotes undo operation

...n/java/org/bigbluebutton/core/api/IBigBlueButtonInGW.java

...ton/core/pubsub/receivers/SharedNotesMessageReceiver.java

...main/scala/org/bigbluebutton/core/BigBlueButtonInGW.scala

.../src/main/scala/org/bigbluebutton/core/MeetingActor.scala

...rc/main/scala/org/bigbluebutton/core/api/InMessages.scala

.../main/scala/org/bigbluebutton/core/api/ValueObjects.scala

...in/scala/org/bigbluebutton/core/apps/SharedNotesApp.scala

.../scala/org/bigbluebutton/core/apps/SharedNotesModel.scala

...button/common/messages/SharedNotesUndoRequestMessage.java

.../java/org/bigbluebutton/red5/pubsub/MessagePublisher.java

...rg/bigbluebutton/red5/service/SharedNotesApplication.java

...va/org/bigbluebutton/red5/service/SharedNotesService.java

...button/modules/sharednotes/managers/SharedNotesManager.as

...ebutton/modules/sharednotes/maps/SharedNotesEventMap.mxml

...gbluebutton/modules/sharednotes/services/MessageSender.as

...uebutton/modules/sharednotes/views/SharedNotesWindow.mxml