#6 Revise directory handling

[Ross Boylan]

I've attached some changes I made to deal with easier finding of files in alternate directories. There are some other changes too; each changeset has a comment. I can also provide this in different formats; the original is in mercurial.

This moves some logic from code into tables.

This is a work in progress, but I figured it was time to share. It addresses some of the issues I raised a few months ago.