Magnolia 5.7 is built on Vaadin 8.4.2

Revalidate: "but DOCS 5.7 refer to Vaadin's 7 line, both in hyperlinks and code examples, mentioning methods that no longer exist in Vaadin 8 docs."

This has to be updated, somewhere maybe just the v7 compatibility hack may help, somewhere the code snippets will need to be rewritten.

See the attached spreadsheet to see where the real problems are.

While on this ticket, let's also look if DOCU-451 could be resolved at the same time.