Fixes to file close and rename actions

* Added walkChildren method to workspace containers to traverse all
children of the container
* Closing a project now closes all open tabs which were open
* Fixed _closeOpenEditor so that it called the appropriate editorarea
function
* Added _renameOpenEditor function which renames the tab of a renamed
resource
Reinstated unlink function

In previous commit, closed files or projects weren't unlinked from the
workspace.
Renamed _preOrderTraversal to Container._workspaceTraversal

Also, removed the sorting of the children of the container
Removed trailing whitespace
Changes to reflect code review

* walkChildren() is now defined on all Resources, not just Containers
* renamed FileOrProjectCloseAction to ResourceCloseAction
Renamed Resource.walkChildren to Resource.traverse
Merge pull request #487 from ovangle/close_action

Minor fixes for close and rename actions.