Wiring date/time search

Summary:
- API: Fix typo in posts 'created_after' variable that breaks search by created datetime
- API: Fix date format used when searching post created/updated dates
- Replace time <select> with from and to text fields, send these in the API request
- Add js date/time picker to date fields

Fixes T261

Test Plan: - Load homepage and search by time

Reviewers: dkobia, eyedol, shadowhand

Reviewed By: shadowhand

Subscribers: seth, sebm90

Maniphest Tasks: T261

Differential Revision: https://phabricator.ushahidi.com/D153