Datetime Calendar Fix

Fixes the datetime calendar not showing issue.

http://eden.sahanafoundation.org/ticket/1193
http://eden.sahanafoundation.org/ticket/1335

Now, datetime calendar shows at all places where Min-Max search is done on datetime type
127.0.0.1:8000/eden/hrm/training_event/search
127.0.0.1:8000/eden/req/req/search