Add support for hierarchy fields in the Page Forms extension

Authored by Fz-29 on Jun 2 2017, 8:23 PM.

Description

Add support for hierarchy fields in the Page Forms extension

This patch introduces default input type as tree for Hierarchy fields, with the values filled in the tree as hierarchical allowed values.
This has been peformed according to the task T161034.

Change-Id: I03bc8cf413ce0969eee6397d652aa5d319a38c86