* Remove uses of `car` and `cdr` in /hy
* Remove uses of `car` and `cdr` in quote tests
* Remove `car` and `cdr` in favor of `first` and `rest`
I beefed up the documentation and tests for `first` and `rest` while I was at it.
I defined `car` and `cdr` in native_tests.cons so the tests read a bit more naturally.