Following @taxi2se's recommendation. This is indeed a focus method, and
Widget already inherits from Focus.Object.
Ping @bu5hm4n who probably wants to adapt this further.
Ref T5363
Summary:
This calendar widget will support basic functionality of calendar.
I've separated this widget from elm_calendar since elm_calendar had
lots of unuseful things inside.
Reviewers: jpeg, singh.amitesh, cedric, CHAN, Jaehyun_Cho
Subscribers: cedric, jpeg
Differential Revision: https://phab.enlightenment.org/D5346