feat(draw-route): implement basic shapes for stencils
feat(draw-route): Add multiple Diagrams support

See #22.

- Diagram class (factory returns class)
- Model class (factory returns singleton, instance)
- Create new Diagrams
- Change/load Diagrams from Model
Merge branch 'stencil-shapes' of github.com:mozilla/seasponge into import-export
feat(draw-route): implement deserialization and load from file

See #22.

- Deserialize and render
  - Model
  - Diagram
  - Element (Stencil)
- Load from file