Branch data for "LEVEL_" and lua branches.

It's amazing how much redundancy and inconsistency can be removed by unifying
this code.  This commit only adds the data in a common format yet.

Conflicts:
	crawl-ref/source/branch-data.h
	crawl-ref/source/dat/des/builder/uniques.des
	crawl-ref/source/mon-pick.cc
	crawl-ref/source/mon-pick.h