Change ContactError to ValidationError, a more general error for all models
Add a basic Group model
Use 'user1' for the user_account in the Group model's tests
Merge branch 'feature/issue-114-fix-odd-things-in-contacts-tests' into feature/issue-112-add-a-basic-group-model

Conflicts:
	test/test_contacts/test_api.js
Merge branch 'develop' into feature/issue-112-add-a-basic-group-model
Allow Group.query to be null
Shorten tests for Group: initialise the group we test against in beforeEach
Merge branch 'feature/issue-112-add-a-basic-group-model' into develop