Fix for parsing error with Dollar Sign ($) in values

Python String template uses '$$' as an escape when a '$' is required
in the value. So add a test case to make sure that works.

Many users end up trying a backslash to escape as well, let's add
support and a test case for that as well

DocImpact

Change-Id: I403cc98505a95f633b5f29ba8f819a2e9c7d58a6
Closes-Bug: #1259729
Merge "Fix for parsing error with Dollar Sign ($) in values"