Refactor Point to Point2D
Created the Display class.

The display class is responsable for the drawing operations.
Display Tests created.

In the Display Constructor the width and height are optional. Not
setting them will result in a canvas of 300x150

In the Point2D class corrected a type in the toString() method.

Removed some garbage from the test_runner.dart

Added Thumbs.db for the ignore files.
Renamed the point_test.dart to point2d_test.dar
Created more display tests.