function/key combo to print the type at point

been wanting this one for ages, but finally found some time on a plane to do it.

I figured this warranted a change to the javadoc keybinding because it never made sense to me why it took `t`.
`ensime-rpc-get-type-at-point` is much, much cheaper since we only need the type name:

```elisp
  (let* ((type (ensime-rpc-get-type-at-point))
         (fullname (ensime-type-full-name-with-args type)))
[...]
```