Added test for provglish.transform.multi_prop_string()

This is only really there to check it doesn't throw an exception.
It doesn't check that the string itself is correct.
Removed the green tags from provglish.template.def_string()

Theese are no longer needed.
FIX: Bindings contain some relationships twice in transform.multi_prop_bindings()

Added a check to see if the relationship was already there. Then had to modify the
coverage function to work without the duplicate relationships.

Also updated the tests to reflect the correctly expected amounts.
Updated version number and changelog.

[skip ci]
Release v0.2.0

See changelog