Shulker's Faithful Factories

• Shulker Factories now generate the spawner tower and finish generation if they grow too close to the boundary of the 9 chunk area around the starting point in which Minecraft allows structure generation. This was the only known issue causing the structure to be cut off at chunk boundaries, so it should always finish generating now.
• Shulker Factories now prefer to generate pieces that bring them back towards the start point so that they don't reach the boundary in which they can generate too quickly, which would force it to stop generation or risk being cut off at a chunk boundary. The farther from the start point, the more it prefers to generate pieces that turn it back to the start.
• Increased the number of generation attempts before Shulker Factories default back to steep stairs.
• Refactored pretty much all of the Shulker Factory generation code to make controlling the spread possible, and to make it simple to add more pieces in the future.

The above changes cause the average number of pieces (incl. platforms, rooms, towers) generated per structure to be greater than in previous versions. A small sample averaged ~30 pieces per factory, with a low of ~24 and a high of 40, however larger and smaller factories are possible. The structure is also denser due to having fewer stairs, and its tendency to resist spreading out. Some pieces, especially restaurants, have become more common due to having less common changes in rotation. For example, since restaurants are currently the only piece which has an exit 180 degrees from its entrance they have become more common as a result of the structure trying to pick pieces that bring it back to the starting point..