Integrate Java class/method resolution with Clojure var lookup.

This allows `cider-jump` to be used on Java class and method symbols just like Clojure vars.

Class, constructor, and static calls are resolved unambiguously. Instance methods are resolved unambiguously when defined by only one class imported by the current namespace. If multiple imported classes have a method by that name, a map of class names to candidate method info is returned.

The counterpart `cider` PR is [#545](https://github.com/clojure-emacs/cider/pull/542).