Binder validation improvements and new routing mechanism

New Features

• DependencyFilter was introduced to make it easier to manipulate the dependencies, more in the documentation.
• New Routing is partially implemented: documentation.
• Dialog component initial implementation is added: live demo.
• Binder automatically updates validation status for each component that implements HasValidation mixin

Breaking Changes

• Fluent api was removed from the components (it will be available later, when the proper API design will be created)
• The Flow documentation got restructured and some urls were updated

All Changes

• https://github.com/vaadin/flow/milestone/49?closed=1