Form Builder support for a `view` mode

[ebruchez]

Right now, if you go to /orbeon/builder/view/12345, Form Builder appears but some features are broken, in particular:

• repeated grids appear garbled
• some actions like deleting a grid crash the client

This involves:

• disabling all buttons and corresponding keyboard shortcuts that can modify the form (save, publish, add control from the sidebar, cut, paste, move…)
• making all the dialogs readonly (Control Settings, Form Settings, Action Editor…)

We have a separate issue, #5983, for returning a 404 or redirecting to edit until this is implemented.

[avernet]

+1 from customer to display the form in Form Builder but make it read-only, e.g. all fields in dialogs are read-only, certain actions (like move, delete, cut, paste) are not available.

[obruchez]

When implemented, make it possible to show a form in read-only mode in Form Builder when a lease is not acquired (currently disabled).