Fix [#66758184] by switching to Query API

The Fog::ServiceInterface code for finding a vAppTemplate
mistakenly found ISOs with similar names.

This commit updates the Core::VappTemplate.get factory to
use the Query API to find the vAppTemplate id explicitly.

Tests are updated accordingly, but remain equivalent to the
previous test. More to be added in suring up commits to follow.
Remove redundant catalog/template methods

These methods were only used to find vAppTemplates in the catalog,
which has now been replaced by a more reliable Query call in
Core::VappTemplate.
Add test for >1 vAppTemplate matched case

This should never happen, as vAppTemplate names should be
unique in their catalog. Better safe than sorry though.
Bump version to 0.0.7, update CHANGELOG
Merge pull request #9 from alphagov/66758184_vapp_template_lookup

[#66758184] Fix vAppTemplate lookup bug