Implement Drag Handler

Trying to learn how to Implement a feature for Dragging  Objects into
CefSharp
Added Missing Include and included missing get sets

The project will build now..  got to figure out what's needed for
DragData.cs and DragOperationsMask.cs
Spacing Corrections

Spacing corrections
Testing Use ability

Completed DragData.cs and DragOperationsMask.cs

When you return true from OnDragEnter I was expecting to cancel all
requests  But if you Drag an image from one url to another it still does
not prevent this from happening.. more research is needed.
One small issue how to handle

Maybe I am over thinking it ... It probably should be handled like this.

http://www.eatoncode.com/shareit/2014-11-28_2031.png

but I still got an issue.
Removed Extra Values I could not get working.
Removed header not needed

It appears that I  did not need to include the cef_drag_handler.h file,
seems to work fine without it.
Added Drag Data Class Back

Need to figure out why DataClass is not accepted
Re-add params to IDragHandler
Re-add DragOperationsMask
Rename DragOperationsMask enum values
Apply flags attribute and implement `Every` option
Rename DragData properties
Populate DragData and pass through to IDragHandler
Revert change to .gitignore
Remove redundant handled variable
Change DragOperationsMask to uint and make Every = UInt32.MaxValue
Use uint instead of Uint32 for consistency (even though they're exactly the same)
Cleanup - Remove CefSubprocessWrapper.h (old file that's not used anymore)
Cleanup - Remove old unused JavascriptBinding files (not used anymore)
Cleanup ClientAdapter.cpp usings
First attempt at implementing CefDragDataWrapper which provides a clr wrapper around CefDragData