Implement Render functions

[fccoelho]

The DengueDiagnostics environment is still lacking render functions.

We can reuse the example Pygame code, or propose a different framework for visualization.

Rendering should also include diagnostic plots, instead of just the grid visualizations, such as

• rewards series
• case series
• test series
• etc.

[fccoelho]

Suggestion:

• Use a color gradient for the squares, to represent the relative number of cases in each square color will be an rgb triplet with green for dengue and blue for Chik.
• generate a curve of cumulative case
• curve of tests
• curve of costs
• other relevant stats