Add Meriv integration.

[Sintrastes]

In addition to simply being able to parse sentences with regard to a schema, the user should be able to make queries via the parsed logical forms of sentences via meriv-core.

[Sintrastes]

Currently montague-reflex is building with meriv-core as a dependency, so long as the right ghc version is chosen.

[Sintrastes]

Currently it seems like building montague-reflex with a true dependency on meriv-core is problematic unless we use GHC 8.10 (at least if we want to use the query API?).

For now, at least to sketch out how the logic programming functionality will work, I am making use of pure-prolog. However, in the future we might either move to using meriv-core -- or potentially something based off of the original bli-prolog prototype, perhaps adapted with a few of the things I learned form meriv-core.

I think we'll definitely want to borrow at the very least some of the time interval code from bli-prolog.

The status of using data types in bedelibry I think is a bit up in the air at this moment. While the meriv-core approach is nice as it doesn't duplicate a lot of code (we can make use of Haskell's functional features), such an approach is probably harder to embed in the targets we care about (e.x. ghcjs, cross compilation to arm).

And it is un-clear how much work it would take to adapt the approach of bli-prolog (e.x. using polymorphic records/variant), as with the current state of that prototype, a lot of things are broken (e.x. type inference of variables for basic rules!).