Efl.Ui.Textpath: support center align for each direction

Efl.Ui.Textpath: support center align for each direction

Summary:
The textpath draws text from the start_angle. User needs to set correct
start_angle to center the text. This start_angle could be changed according to
each parameters of circle_set such as x, y, radius, direction and text itself.

So this patch is introducing direction EFL_UI_TEXTPATH_DIRECTION_CC(W)_CENTER.
The center of textpath will be located at the start_angle with this direction.

Test Plan: I will add example if this patch is acceptable.

Reviewers: Hermet, jsuya

Reviewed By: Hermet

Subscribers: cedric, #reviewers, #committers

Tags: #efl

Differential Revision: https://phab.enlightenment.org/D8892