Compare stdlib functions to OCaml

[pbiggar]

Though we had many implementation of the stdlib functions in F#, I hadn't tested them against the OCaml implementations to make sure there was no unchanged behaviour.

I added an API to run Dark code in the OCaml implementation and to compare the output to the Dark implementation. I hooked it up to the fuzzer and also to the existing unit tests. Then I went through all the existing functions and made sure the results were the same, occasionally fixing bugs in the F# implementation and adding notes about next steps once the F# implementation ships.

While I made as much bug-for-bug compatible as possible, I did aim to make error messages identical.

Fixes:

• error message on Date::parse
• support % for Int::mod
• string.replace works when the argument is ""
• Date functions now give negative dates for before 1970, like the OCaml versions
• fix String.toInt around the 2^62 boundary
• fix signature of Int::remainder
• implement List::contains and List::member, with tests
• remove List::all as it's not in the OCaml version
• fix tests of Int::random
• handle NaNs, and different ordering of parameters, in Int::Clamp
• add list tests
• make the implementation of Record creation identical to OCaml
• make the implementation of List creation identical to OCaml
• fix List::head_v2, List::tail_v0
• don't check list length on List::last_v0
• implement DB:: queryOneWithExactFields::v0 and DB:::generateKey
• normalize strings when they are created (fixes a lot of "Z̤͔ͧ̑̓ä͖̭̈̇lͮ̒ͫǧ̗͚̚o̙̔ͮ̇͐̇" tests)
• fix String::random_v2 signature, and add many more random tests
• fix String::first and add simpler implementation
• add many many string tests
• fix String::slice which has some edge cases
• fix String.split which has lots and lots of edge cases
• fix String::toUppercase and String::toLowercase
• fix String::slugify_v{0,1,2} and add lots of tests
• fix String::replaceAll
• Port String::base64Decode

Other changes:

• ported the type checker
• improve error message on incorrect arguments
• support other arguments in scripts/run-fsharp-tests
• port AST traversals
• normalize arguments between implementations by parsing the OCaml exception messages
• remove old README
• add support for FSHARPONLY and OCAMLONLY tests (mostly to add two implementations for different error messages)
• support sending userfunction parameters to OCaml
• add all the Test functions to OCaml
• split the OCaml libraries so that the backend libraries are not in libbackend anymore
• rename libserialization to libocaml
• add Test::inspect
• add execution functions to be used in the fsi
• add Test::toChar