Handle update correctly about faro HOT 3 OPEN

@nakulshah87: Have changed update APIs to include version verification. Also, API to change control flag has now been included with update API call. Also, have changed the Event.java interface. Now there will be a BaseEntity which will provide "id, version" to every Entity class(Event, Activity, Poll etc.)

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@nakulshah87: Activity completed. Please verify interface changes.

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@nakulshah87: Poll completed. Huge changes in API for Poll updates. Namely, I have removed the "cast vote" API and have included it in the "updatePoll" API. Here is an emulated workflow involving regular Poll property updates and cast vote updates: https://github.com/gorillapie2000/Faro/blob/master/Backend/src/test/java/com/zik/faro/functional/FunctionalPollTest.java#L117

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