Stop depending on AddCaches

That's broken anyway.
More examples in worksheet
Add AddCaches2: New attempt at static caching

This is much better, but I do eta-expansion of primitives at the wrong
time, so AddCaches2.extendReturns can't special-case them as it should.

AddCaches is commented out.

AddCaches2 is a separate component, not a mixin at all: it does not even
inherit from ANormalFormStateful.

Warning: Worksheet output generated with TypeChecking = false.
AddCaches2: 1st version with decent results

There are still bugs, but that's still progress from "the implementation
is completely broken".

This still requires TypeChecking = false though (as set here).
I'll need to see what to do about that.
Fix bug with nested Abs
AddCaches: Remove commented out code