Reimplemented StructureRequirement
	--> Structure requirement must only store the current layer and is planned to get that change
	--> Materials that can't be gathered by player (Like AIR) should be ignored in near future
Added UnsupportedStructureException, will be thrown when a schematic contains an unkown material
Added InvalidStructurePlanException, will be thrown when a plan doesnt contain valid values
SchematicReader, StructureReader, StructurePlanRegister not anymore static