domain package:
* theorems are stored in the theory
* creates hierachical name space
* minor changes to some names and values (for consistency),
e.g. cases -> casedist, dists_eq -> dist_eqs,
[take_lemma] -> take_lemmas
* separator between mutual domain definitions changed from "," to "and"
* minor debugging of Domain_Library.mk_var_names
Test examples ran successfully