Refactored Arrange interface: remove the union based BedShapeHint, replace it with proper function overloads
WARN: this commit is only intermediate, it does not compile.
DynamicPrintConfig::full_print_config()
new cheaper constructors of DynamicConfig / DynamicPrintConfig from ConfigBase
Unit tests: ported test_model from upstream Slic3r, thanks @lordofhyphens
Unit tests refactored to use less autos and initializer lists for readibility,
DynamicPrintConfig is handled by value, not by shared pointer.