Implement text-based planet id deduction
Implement planet image handling stub
Decrease self-repeating in Controller code
Implement properties pane stub
Represent Solar System as a model object
Begin connecting model and view
Convert images to PNG

Add transparency layer and scale down big images
Refactor object image creation
Decrease self-repeating in Controller code
Make image size dependent on object radius
Normalize image sizes
Move boundingObject property to OrbitCharacteristics
Add data about Solar System objects
Refactor astronomical objects' fields

Before, mass and radius were optional;
now, they are required for the constructor.
Add null-check for the retrieved object
Create a PhysicalCharacteristics class
Refactor AstronomicalObject content division
Add json-simple library to read text data
Remove flexjson library (impractical approach)
Correct missing return types in Builder class