Added more Linq2Xml helpers to TooltipHelpers
Added Drag and drop support to move F# project items within the same project
  Dragging non project items and dragging out of project results in default base behaviour.
Modified search so that PRojectFiles within folders are found.
Also added crude folder ordering, this is by no means final code.
Current problems: moving from one folder to another doesnt yet work due to the virtual folder prefix not being added to the nodes Include attribute.  You can move a file inot another folder, and then drag move to a new location within a folder.  Its also possible to disable inter folder moving if required.
Remove the ability to drag before/after between different tree elements:
You must be within the same tree.  Dragging into another node if still performed as usual.
Fixed the Folder Comparison order using occurance within project file.
Merge pull request #228 from 7sharp9/DragAndDrop

Drag and drop Support