Implement and() & or()

[Reference](http://postgrest.org/en/v7.0.0/api.html#horizontal-filtering-rows).
- `and()` & `or()` directly refer to the conditional statements AND & OR respectively.
- Although functionality for `and()` already exists through chaining functions, the use case for it would be to allow complex chaining of both `and()` and `or()` together.