Removed dead codes and unreferenced variables

#### Background
This submission is meant to address this task: [MAGN-255 Remove dead codes in DragCanvas](http://adsk-oss.myjetbrains.com/youtrack/issue/MAGN-255)

Most codes in DragCanvas.cs (and few other files) were made redundant after the introduction of StateMachine in late September 2013. These codes were disabled with a preprocessor (#if false) and has been preserved just for referencing purposes. Now that StateMachine has been tested for a sprint, it is time these dead codes are removed from the source codes.

Few unused variables have also been removed alongside this change to avoid compiler warnings.

#### Testing
There is no testing necessary for this change, the codes removed were not compiled anyway.