ace-window.el: add move and delete functionality

* ace-window.el (aw-generic): New macro.
  (ace-window): Do different things depending on prefix arg.
  (ace-delete-window): New interactive function.
  (ace-select-window): New interactive function.
  (ace-swap-window): New interactive function.
  (aw-switch-to-window): Test if argument is window.
  (aw-delete-window): New function.
  (aw-swap-window): New function.

Fixes #2.