[Fix #444] Add command prelude-update-packages
New keychord xx -> execute-extended-command
[Fix #447] Extract ido config into a module

This should make it simpler to disable ido completely if you want to use
an alternative library (like `icomplete` or `icicles` for instance).
[Fix #451] Add the ability to preload personal code
Fix typo in prelude-ido
Merge pull request #452 from jjcomer/master

Fix typo in prelude-ido
Merge remote-tracking branch 'upstream/master'

* upstream/master:
  Fix typo in prelude-ido
  [Fix #451] Add the ability to preload personal code
  [Fix #447] Extract ido config into a module
  New keychord xx -> execute-extended-command
  [Fix #444] Add command prelude-update-packages