add BuildCraft API triggers for Botania

Some notes:
- A few textures need to be made. In textures/items: triggers/manaDetector, triggers/manaEmpty, triggers/manaContains, triggers/manaSpace, triggers/manaFull and triggers/runeAltarCanCraft.
- A few lines of code now depend on the existence of buildcraft.api.transport, which carries in the other APIs. It would be nice if those were bundled in the JAR.
IconHelper.