Adds parameter_groups to HOT specification.

The ability to group and order parameters in the template is
currently missing. This patch allows for a new section of the
template, parameter_groups, to be added by the template author
to explicitly define the expected behavior.

Change-Id: I6d8dc4e6490fbfe9cc45f6ca9cb1ac2826e13273
Implements: blueprint parameter-grouping-ordering
Merge "Adds parameter_groups to HOT specification."