hoversel: add item disabling support.

hoversel: add item disabling support.

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    hoversel: add item disabling support.

    Summary:
    Hoversel items can be disabled using elm_object_item_disabled_set
    @feature

    Test Plan: elementary_test

    Reviewers: prince.dubey, shilpasingh, raster, Hermet, conr2d, cedric

    Subscribers: poornima.srinivasan, rajeshps

    Differential Revision: https://phab.enlightenment.org/D3122
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Signed-Off-By: Jee-Yong Um <jc9.um@samsung.com>
Change-Id: I12d1d99b07f85d4abebea7967006e8cd2d15c16c