[WiP] Elm 0.19

[vjousse]

Fixes #202

Still a work in progress. First step, make it compile, even if not half of the feature are present. Second step, make it work as expected.

• [x] Make it compile with elm 0.19
• [x] Add useful date formatting back for formatDate function
• [x] Add scrolling behavior back to src/Command.elm
• [x] Update to elm/http 2.0.0
• [x] Add Keyboard behavior back in src/Subscription.elm using https://package.elm-lang.org/packages/elm/browser/latest/Browser-Events
• [x] Fix textContent function in src/View/Formatter.elm
• [x] Add WebSocket support using ports
• [x] Change tests to work with latest elm-test
• [x] Replace Autocomplete with https://github.com/ContaSystemer/elm-menu/tree/1.0.2
• [x] Update cleanErrors in src/Update/Error.elm