Harmonize how REST API handlers get a JSON body

Give the ability to any handler to get a JSON body which
can contain more information about the event. The indexing
is given a proper event object with the timestamp of when the event
was generated on the source node.

Preparation work to be able to automatically detect inconsistencies
between the object to be indexed and the real status of NoteDb.

Change-Id: I966cf259d68605a7acc54c47bf872b2ed2296162
21 files changed