Add attributes_get for widget item.

Add attributes_get for widget item.

  Add widget item to provide attribute for style.
  This is also an upstream code.

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   efl_access: Add attribute_append, attributes_clear APIs

   Summary:
   Add attribute append and attributes clear API, attributes of widget/widget_item helps in adding additional information
   about the widget/widget item in the form of key-value pair.

   Test Plan:
   Query the attributes using atspi_accessible_get_attributes in atspi_client and an hash table consisting
   of updates attributes should be returned.

   Signed-Off By: Shilpa Singh <shilpa.singh@samsung.com>
   Signed-Off By: Lukasz Wlazly <l.wlazly@partner.samsung.com>

   Reviewers: kimcinoo, lukasz.stanislawski

   Subscribers: cedric, govi, rajeshps, jpeg

   Differential Revision: https://phab.enlightenment.org/D5510

Change-Id: I5c64828b8accab550c980b0f4a80e7bc4770413e