Add keyword autocomplete jQuery widget
Made JS Rpc object methods chainable
Field definition improvements

Added visibility and value restrictions to status, resolution and
product specific fields.
Field visibility controls in JS
Refactoring and various fixes in Bug JS object

* All publich methods which require field accept eiher field name or
  field description object
* Alerts from Bug objects can be disabled (probably will be removed
  completely at some point)
* Bug.fd() class method removed and replaced with field() object method