Create one parameters wrapper tag for all release params

Ensure only one parameterDefinitions XML tag is created for the entire
set of parameters instead of one per parameter.

Add a test case to show the correct behaviour with more than one
parameter defined and update the docstring to use the yaml test case as
an exmaple. While updating the docstring add missing default values for
arguments.

Change-Id: Ife8f2535117d355d845d5d72dd9e6e6669a6b9df
Merge "Create one parameters wrapper tag for all release params"