Redesign Special:Search:

Redesign Special:Search:
* remove all horrible long messages that just kept being sticked on the search page. There is
  no reason to show long messages on *every search* to *everyone*, use the Help link instead
* organize search options into a straighforward menu on right side of search box
* Search box now comes with a header for quickly switching between typical namespace groups:
  - Articles - wgNamespacesToBeSearchedDefault namespaces, default for anons
  - Articles/Project - wgNamespacesToBeSearchedDefault + wgNamespacesToBeSearchedProject,
    default for logged-in users. Contains namespaces like main, user, project, etc..
  - Images - local/commons images
  - Everything - quick link to search *all* namespaces
  - Advanced - this will show our powerbox, which is now not shown on every page

Preferences change:
* logged-in users by default search more namespaces than anons, this relies on assumption
  that logged in users are more likely to be regular contributors in a community, and
  thus be interested in community stuff as well as articles

* bug 14609, if users leave their namespaces settings on default, changing default
  search namespaces will change users namespaces as well

Images:
* bug 5101. Don't hide commons images as broken links if search backend is smart enough to
  return them.