ExtendedComboBox.js, ExtendedLovCombo.js : modified resizeToFitContent() to have a 'light' version, which does not call restrictHeight() if there was an 'update' of the store, which in turn prevents scrolling to top issue

ExtendedLovCombo.js :
- very important fix to onTypeAhead() in order for it to work correctly (prevent any action if the store is not filtered)
- selectAll() overriden to call doQuery() to show the full list only if the store is filtered, otherwise causes flickering