Build on hackage

[m4lvin]

See https://hackage.haskell.org/package/smcdel-1.2.0/reports/

Now that #30 is fixed, i.e. we can build with cabal, the problem here is a bit different: the failure on Hackage is because the cudd fork is not available there.

Building on Hackage is also a goal in order to get the Haddock documentation built there too #25

[m4lvin]

Chosen solution in 771ad7a:

• make building the CUDD parts optional using Cabal flags and conditional blocks

This may not be the "right thing to do" because apparently the public API of a package should not depend on its compile flags. But on the other hand, there are no (public) dependencies of SMCDEL at this point anyway.

At this occasion we also make building the web interface optional behind a build-flag, so that a regular stack install smcdel will need a lot fewer dependencies.

Discarded alternative ideas:

• fork cudd and upload cudd25 or similar to Hackage --- Not very elegant, as it would be nice to move from 2.5.0 to 3.0.0 later anyway.
• Move all CUDD stuff into a separate smcdel-cudd package --- would run into the danger of getting outdated.

[m4lvin]

It's a mystery. Now https://hackage.haskell.org/package/smcdel-1.3.0/reports/ says:

Status: Built successfully.

No reports available.

🤔

Maybe this is because I uploaded documentation manually? Does Hackage then not build anything?