Return objects in all json responses

[mconf-daileon]

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Author Name: Leonardo Daronco (Leonardo Daronco)
Original Redmine Issue: 633, http://dev.mconf.org/redmine/issues/633
Original Date: 2013-03-12

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Review all json responses to standardize the returned objects.

Currently, most of them return a json object with a message only. We could replace it by the object that was created/updated or by an empty object in actions that destroy the objects.
Returning the object is useful when updating it via json, like is done when jEditable is used. In an update, for example, it expects the object to be returned so that it can confirm that the new value of the attribute it tried to set was actually set.