Better Boilers

Now that the 1.0 is out, I can focus on improvements to the boilers and preparing for larger updates. In this version:

Gameplay-wise:

• Added configuration for steam boiler properties.
• Multiplied the steam boil rate by five.
• Made slight modification to boiler block textures.

Code-wise:

• Moved multiblock-scanning code into an abstract class to prepare for future controller types.
• Made water consumption dependent on steam production value in config