Add 'apro' variant of 'apropos' that returns symbols with namespaces

This is probably not in a form that you would want to include, if you are interested in including it in the first place.  Suggestions for changes welcome.  No problem if it isn't of interest.  Just close the issue.

In particular, I was guessing on how to make symbols usable in reply, like help and cdoc.

Examples of output below.  Compare against output of similar apropos calls for the difference.

user=> (apro "replace")
(replace
 clojure.string/replace
 clojure.string/replace-first
 clojure.walk/postwalk-replace
 clojure.walk/prewalk-replace
 clojure.zip/replace)
nil
user=> (require '[clojure.string :as str])
nil
user=> (apro "replace")
(replace
 clojure.walk/postwalk-replace
 clojure.walk/prewalk-replace
 clojure.zip/replace
 str/replace
 str/replace-first)
nil
user=> (in-ns 'clojure.string)
#<Namespace clojure.string>
clojure.string=> (user/apro "replace")
(replace
 replace-by
 replace-first
 replace-first-by
 replace-first-char
 clojure.core/replace
 clojure.walk/postwalk-replace
 clojure.walk/prewalk-replace
 clojure.zip/replace)
nil