Change list formfield to disable chosen when facing a huge amount of options

See Feature Tracker:
http://joomlacode.org/gf/project/joomla/tracker/?action=TrackerItemEdit&tracker_item_id=31514

Chosen has performance issues when facing a huge amount of options. Since the menu item view (like most views) use `JHtml::_('formbehavior.chosen', 'select');` to load Chosen on every `<select>`, this can break the creation of menu items.
This PR makes use of the default behaviour of `JHtml::_('formbehavior.chosen');` which triggers on the class `.advancedSelect`.

This PR will do a few things:
- Changing the list formfield so it defaults to the class "advancedSelect" if no class is given. Currently there is no default at all.
- Changing the list formfield so it removes this class if there are more than 10'000 options.
- Changing the call `JHtml::_('formbehavior.chosen', 'select');` to use the default `JHtml::_('formbehavior.chosen');` in the menu item view.