The Plans 'Request Feedback' has been relocated from the Share form to a ...

separate form.

Changes:
 - Removed "Request feedback" from the _share_form.html.erb partial and
created a new partial _request_feedback_form.html.erb.
- Added a tab to Plan _navigation.html.erb for 'Request feedback'.

Fix for #2234

Issue 1845 (#1846) ...

* Fix bug preventing Feedback from being requested

* Fix Rubocop violations

* Extract feedback requests into own controller

* Add test for feedback requests

* Fix Rubocop violations