Adds support for MaxWeight on containers

[merschformann]

Description

Adds support for adhering to a maximum weight capacity on the containers. Every piece may expose a weight that cannot exceed the maxWeight defined on the container. By default, pieces weigh 0 and containers have infinite weight capacity.

Changes

• JSON: Introduced weight on pieces and maxWeight on containers.
• XML: Introduced attribute Weight on pieces and attribute MaxWeight on containers.
• The weight is only used for the maximum container weight calculation, no stability calculation considers it and it's not further broken down into cubes of a piece.
• All heuristics and model formulations were updated to adhere to the new constraint.
• Fix a bug with single piece instances in MIP models.