CppEditor: introduce include hierarchy

Based on type hierarchy.

Added to context menu ('Open Include Hierarchy')
Shortcut(Ctrl+Shift+I)

'Include Hierarchy' contains:
FileName for which 'Include Hierarchy' is done
Includes(which files are included by current file - tree hierarchy)
Included by(which files include current file - tree hierarchy)

It is possible to open/goto each file by clicking on specific item.
Additionally for 'Included by' files it goes to the line where is include
directive for current file.

Change-Id: I549b1ed64e4c9f6955f60d00efb12950a3259f81
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@digia.com>