[Do not merge] Add deep category field

Authored by Tonina_Zhelyazkova_WMDE on Apr 9 2018, 2:25 PM.

Description

[Do not merge] Add deep category field

Bug: T170533

Some code was reused from Upload Widget where the same functionality is present.

Change-Id: I97de0ff2420c945c4ae6a1894e87c1780ebc73eb

Details