Doesn't really make sense to have the additional IDocument *editorDocument()
method.

Change-Id: I0a7420eb1afaa76f63c3f7e9c4b373acf624ffb9
Reviewed-by: Eike Ziller <eike.ziller@digia.com>

For "includes" we should use snapshot from "SnapshotUpdater"(project
specific snapshot, not global snapshot) instead of "global" snapshot.
The snapshot of the editor's SnapshotUpdater contains the documents
parsed with the appropriate include paths/defines etc. and should
therefore be used for the include hierarchy.

Change-Id: I6bbaf5040536b771d32697aad1db364758ff8382
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@digia.com>

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>