Fixes mcb package and mcbconv to include the full block id in
the converted world data. This means the primary id, as well
as the sub id.

The mcb.Block type now has the Id field of type Id. This type
has been moved from the mcra package into mcra/mcb for this
purpose.

mcmapgen can now accurately differentiate between things like
wool blocks or different colours. Previously it would just
render the standard white block, as the sub id was lost during
the map conversion stage.
Removes debug output.