Avoid some error in tests: ActionView::Template::Error: uninitialized constant PatchingProjectModel::IssueTemplate
Fix validation failure in unit tests
Fix 'template_title' duplicate value in fixtures, forbidden by model/db validation
Explicitly declare some more needed fixtures so that the test can be run alone
Add some reminder comments to test/functional/issue_templates_controller_test.rb
Fix validation failures in test/functional/issue_templates_controller_test.rb
Fix validation failures in test/integration/issue_templates_test.rb