ivy.el (ivy-dispatching-done): New command on "M-o"

ivy.el (ivy-dispatching-done): New command on "M-o"

* ivy.el (ivy-minibuffer-map): Bind "M-o" to `ivy-dispatching-done'.
(ivy-action-name): Update, all actions are now in hydra's format - key
binding, command, hint.
(ivy-read): The default action is bound to "o" in the dispatch.
(ivy-switch-buffer): Update to new action format.

* counsel.el (counsel-locate):
(counsel-rhythmbox): Update to new action format.

The new interface allows to do whatever you want with the selected
candidate with a very short key binding.

The old interface with "C-o w/s" still works, but:

- it gives a lot more info than necessary for only selecting action
- doesn't scale well with the number of actions: for 10 actions you
  would cycle "w/s" a lot.

Example with `ivy-switch-buffer':

- switch to selected buffer: "C-m"
- kill selected buffer: "M-o k"; you get a hint right after "M-o".

When there is only one action, "M-o" will forward to "C-m".