Provide component level tests.

[dbrnz]

In particular for the main editor component, with tests to include:

• Adding a component.
• Moving a component.
• Adding two components and creating a connection between them.
• Moving a single connected component.
• Moving multiple selected components.
• Deleting a component.
• Deleting a connection.
• Deleting multiple connected component.
• Moving a connection's control point, for both rectilinear and linear connection paths.