Allow converting Names to Terms directly
Fixup comment
Minor worksheet changes
Allow Types as base ValType in CBPV

This allows sticking normal types inside CBPV terms. While this is
(mostly) sensible (except for type variables), importing constants is
much trickier.
+Feature: Convert CBPV types to CPS types
More work on CPS WIP

There was a "typo" in the term transformation; but most importantly, I'm
utterly unable to write down the transformation on types by just
hacking. I ended up generating untyped terms and using type inference on
them again, which at least seems to work.
CPS WIP: More testing
Use Name for names in UntypedSyntax etc.

The previous code used instead String for names; this is ugly, and
annoying whenever one needs to convert Terms to UntypedTerms and thus
Names to Strings (as in the current CPS transform).
Do this also in PrettySyntax.
Allow converting also Name to UVar

After the previous change, one can *almost* always replace String by
Name when building an UntypedTerm; *almost* because there was no
implicit conversion from Name to UVar, before this commit.
Don't convert Names to Strings during CPS conversion
Better message for type errors in applications
Add facility for showing terms
Finally fix typed CPS transformation

This wasn't so hard, after I got better error messages and started
thinking more carefully. Names are still awful.
Reenable typechecking

To fix the CPS transformation, it helped to enable *more* typechecking
to get errors earlier.
Cleanup type construction in inference
Cleanup: rename fields to better names
Change pretty-printing for type variables (WIP)

This might make error messages worse. We probably need to split toString
and pretty-printing also for types.
Cleanup CPS code a bit
CPS: rename functions
TODO