Fix several new bugs introduced by D487, refs T851

Summary:
- Base.yml had incorrect group assignment for one attribute
- attribute search was not being limited by form
- attribute search was including invalid conditions
- default search conditions would cause ambiguous column errors

Test Plan: Was checking the API manually. Behat tests need to be updated.

Reviewers: aMoniker

Subscribers: vladimir, rjmackay

Maniphest Tasks: T851

Differential Revision: https://phabricator.ushahidi.com/D513