Improve form wizard, refs T42

Summary:
- set different icons for different inputs
- move editor into left pane, switch between add/edit mode
- right pane acts as preview and reorder only

Test Plan:
- try the form wizard
- add new inputs
- edit inputs
- delete inputs

Reviewers: dkobia, eyedol, rjmackay

Reviewed By: rjmackay

Subscribers: srutto

Maniphest Tasks: T42

Differential Revision: https://phabricator.ushahidi.com/D201