Sync minion-list every 30s

Refresh the list of active minion every x sec.

Some comments:
 * not sure why you wanted to append the list of _result.
 * the timeout number settings (30 sec) needs to be put in a central configuration somewhere.
  * work in Firefox and Chrome (Chrome does not work if I move the "setInterval" line into saltui.js (anyway it was probably not the right place. Maybe because Chrome requires the dom to be in a ready state ?).

My idea is to merge a list of all minions (from pillars ?) with the list of active responding minions.

As a note (nothing to do with this pull request) I have realized nothing works with IE 9. Apparently dataset is not supported.