Implement the point, line and map interfaces

[closedspace]

Summary

Currently we only draw a simple grid with the ability to add circles on each grid square and the existing code is not properly split up. We should implement a Point, Line and Map interfaces and have them integrated in the drawing process.

Acceptance Criteria

1. There is a Point interface that holds integer coordinates, a color and a draw method.
2. There is a Line interface that holds a list of Points, a start Point an end Point and a color
3. There is a GridMap interface that holds a list of lines.
4. Each interface is in a separate file

[tdemkowski]

Sounds good. I'll note that

• When we define a FlowFree map (to be solved), we use a pair of coordinates
• For our line, the "start" point can be defined as the first point (from the pair of coordinates) selected to draw a line.