Added type-cheking assertions to gUnit.

Added methods assert(value) hasType (DesiredType) and
deny(value) hasType (UndesiredType) to gUnit.
Web dependencies added to Makefile.

Added the files included by js/index.html to
the list of dependencies for the web build.
This should make sure that all files on the server
are updated.

Also added a rule to get ace.js, since its absence
will now cause the make to fail.
Added more methods to collections.

Included sequence methods and conversion methods.
Explanded the applicability of list.at(ix)put(v) to
case where ix = list.size + 1 (which was formerly a bounds
error.
Exported types in StandardPrelude, and corrected name to sequence.