Listing components and data sources

New features:

• New listing component implementations
  • NativeSelect
  • ComboBox
  • CheckBoxGroup, replaces the multi select version of OptionGroup
• RichTextArea with the same ValueChangeMode support as TextField/PaswordField
• Binder enhancements
  • Support for binding to single and multi selects
  • Binder.hasChanges() for checking if any field value has been modified
  • Errors are cleared after loading or binding a bean
• DataSource.refreshAll() for making a data source reload all data
• TestBench queries now find both old com.vaadin.v7.ui and new com.vaadin.ui components

List of all changes: vaadin/vaadin@8.0.0.alpha1...8.0.0.alpha2