Dependencies: Remove unnecessary 'funcool/cuerdas' dependency

[yogthos]

Cuerdas was used for its nil handling, switching to clojure.string is fine, but the nil checks need to be added in.

[yogthos]

Out of curiosity, what's the motivation for removing cuerdas, and doing nil checks manually. I looked through the code and there are a number of namespaces that will need to be updated. I find this is overall more error prone, as it's easy to miss the nil checks.