replaces log grades and merchantability parameters in keyfiles with variant-specific {{include.var_merch}}

also adds include files for all variants, BM_merch.txt, CA_merch.txt,
etc.
replaces pine and spruce beetle ratings in keyfiles with {{include....}}

also adds pine_beetle.txt and spruce_beetle.txt to include folder
cleanup comments, replaces species diversity in keyfiles with {{include.var_diversity}}

also adds var_diversity.txt for each variant.