Feature/update verona metadata

- Send metadata as voeReadyNotification to host

Displaying a message is task of the host
#398

- There is a page navigation only for not always visible pages
- Fix initialization of the button's action parameter

- Prepare usage in editor
- Remove test from ScrollPagePipe, because the call to "new Page" expected
  the initialization of GeometryComponent

- Remove css margins of floating keypad

- A floating keypad is generated inside a div with the class
  'cdk-overlay-pane'. Now the position of this div is updated when
  dragging the keypad.

- Add spans with 'nbsp;' to images to be able to align drop lists of
  cloze elements with images to the baseline.

- This prevents the cursor to be set to the upper left corner of the
  preview image

- Allow put back
- check if to replace item can be moved elsewhere. this is only possible 
if it is not in it's origin.