New Event uuid column and autoincremental id

Re added the autoincremental id column for the Event table, and added a
new column to store the event uuid. The uuid will be exposed to the user
as the id of the event, but internally the event will be handled using
the value of the id column.

Change-Id: I43464c6079bf7631fda0c4ab112b8f874c6190a3
Co-Authored-By: chmouel@enovance.com
Closes-Bug: #1261883
HOT templates get_param allows extra attributes

HOT templates now allow the use of extra attributes for the
get_param function. With this change it is possible to traverse complex
parameters.

If one of the extra arguments does not match with a key or a valid
index, an empty string is returned.

Change-Id: I49f46b164fd21f6cc7dcea8d4ec1046f6cc912b3
Implements: blueprint hot-select
Merge "New Event uuid column and autoincremental id"