efl_ui_clock: Merge datetime/dayselector/clock widgets into efl_ui_clock.

efl_ui_clock: Merge datetime/dayselector/clock widgets into efl_ui_clock.

Summary:
Datetime widget is module based, so datetime widget is used as base for efl_ui_clock and merged dayselector/clock features into efl_ui_clock.
Added day selection and seconds support in efl_ui_clock.
 Added clock features like auto updation of time, stop timer etc in efl_ui_clock.
 Added API to enable/disable edit_mode. efl_ui_clock can be configurable to display either only day/date/time or display any two of them or display all three.
Added efl_ui_clock.c and test_ui_clock.c. Theme and Module is added in another patch by Amitesh.

Original author is Yeshwanth <r.yeshwanth@samsung.com>. I have polished this patch a bit and make it compatible with current EFL code.

Test Plan: test_ui_clock

Reviewers: bu5hm4n, tasn, yashu21985, jpeg, cedric, raster

Subscribers: CHAN, woohyun

Differential Revision: https://phab.enlightenment.org/D3938