Performance tweaks and bug fixes.

  Performance tweaks!
  - color_get_schemes(), color_get_theme_info(), color_compatible(), color_get_palette() all use static variables.
  - removed the extra $themes = list_themes(); in _color_rewrite_styleshet()
  - moved code around in color_form_alter() to only retrieve themes and include algorithms when needed. (~40-50ms performance fix)
  - Only taking need columns (id, name, hex) from schemes in color_get_theme_info()
  - fixed support for garland/minnelli screenshot on /user/{uid}/edit
  - fixed admin/build/themes/settings/{theme} to correctly set theme name
  - Cleanstate: fixed up cleanstate a bit.
  - Fixed default variable_get('cache') variables to fit the "Disabled" mode in admin/settings/performance by default.
  - Fixed notice with Undefined indexes by using isset()
 
  Unfinished:
  - Custom preview.inc option. Currently, if you provide a preview.inc in the theme's /color folder, the default will be overridden.
 
  Bugs:
  - Without user_access('select different theme')) and select color scheme users can pick schemes w/ block but not user profile.