New Components: CheckBox, ComboBox and SplitLayout

New Features

• VaadinCheckBox
• VaadinComboBox
• VaadinSplitLayout (new demo might not be yet deployed)
• Component events now return the actual component type (e.g. VaadinComboBox) for getSource() instead of generated component (GeneratedVaadinComboBox)
• Generated Components slot methods now have Fluent API

Demos & New Tutorials

• Flow Components demo is published now
• Tutorial on starting to use Flow Components

Breaking Changes

• ModelConverter method has been renamed
  • Now P toPresentation(M modelValue) instead of toApplication(M modelValue)

Fixes

• Navigating back doesn't crash the app anymore in certain cases #2089
• On production mode, client side logging is now disabled
• Template parsing ignores comments