Normalize the structure of files (XML vs ZIP vs HTML)

[ronaldtse]

• We want to integrate the HTML pages into the site natively.
• ZIP files should be generated dynamically (if this is still desirable)
• All the XML files shall remain in position but the rest should be nicely structured so that we can show some metadata of each schema.

[ronaldtse]

This also applies to def.isotc211.org.