edje: add edje_object_color_class_clear()

edje: add edje_object_color_class_clear()

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commit c963a0f9cb3009b7ad1a5cdc623b0d7c9f8d3e4f
Author: Jee-Yong Um <conr2d@gmail.com>
Date:   Mon Jan 4 15:10:58 2016 -0800

    edje: add edje_object_color_class_clear()

    Summary: clear all color classes defined in edje object

    Reviewers: raster, jpeg

    Subscribers: woohyun, cedric, kimcinoo

    Differential Revision: https://phab.enlightenment.org/D3514

    Signed-off-by: Cedric BAIL <cedric@osg.samsung.com>
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Signed-Off-By: Jee-Yong Um <jc9.um@samsung.com>
Change-Id: Ifae7a3b2672ed416a6707ac70e2b81c975caf421