Define origin of compat. closure
Throw out unused lamfold
Add some comments and remove duplicates / rename lemmas in Beta

More clarity.
Tidy up the Eta module

Reorder the way some lemmas appera, give more consistent names.

Also, add more comments.
Add more comments in Subst
Document and tidy-up Postpone module

Add comments and move one lemma to Eta
Merge pull request #21 from knuton/comments_and_cleanup

Comments and cleanup