Reworks Node validations

This makes use of the mandatory option and complex types of WSME to
remove some of the custom validation code. The patch also includes a
new attribute on Nodes API object called chassis_uuid to store the UUID
of the chassis that Node belongs to, once this field is set it magically
converts the UUID to the numeric ID of the chassis and sets the chassis_id
attribute to be used internally.

Change-Id: Ie51761a3b9a018d101a6335ea7bafb09393816d4
Closes-Bug: #1252213
Partial-Bug: #1223847
Merge "Reworks Node validations"