Understand block families, shapes, and collision

[skaldarnar]

This is what @jellysnake and I figured out:

• symmetric block family won't rotate
• horizontal and freeform will rotate
• default block shape is engine:cube
• default block family is freeform or horizontal
  • except if the shape has no collision field, thenb the family seems to be symmetric
• thus, collision defines the rotation properties

Precedence: family specified (use that family) > shape specified (derive family based on collision) > nothing specified (default to engine:cube shape, thus no collision, thus no rotation)

[skaldarnar]

Another thing noticed with regard to StructureTemplates:

• when the block family is horizontal a rotation has to be specified when referencing the block, it won't show up without it (see https://github.com/Terasology/HjerlHede)