content model in multiple languages

[sydb]

The “Content model” section of element tagdoc pages currently shows the PureODD <content> taken directly from P5; the “Schema Declaration” section that is present in the current Guidelines tagdoc pages is not present in this eeditiones version. I think the two sections should be rolled into one: the “Content model” section should have a mechanism (buttons, drop-down, whatever) for the user to select ODD, RELAX NG (XML), or RELAX NG (compact).

One could even make an argument that DTD or W3C Schema should be available, too. But I would not make that argument, as I want to actively discourage new users from either of those languages.