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.
Same deal for this class.