Organization of the CalDAV Use Cases document

[anermina]

The original CalDAV Use Cases document organizes use cases into separate subclauses. However, a numbered list might be a more suitable option for the third-level subclauses.

This is currently encoded as it appears in the original document. If any adjustments are needed, please let me know.

Similar applies to January 2005 CalConnect Interoperability Test Scenarios.

[ronaldtse]

@anermina lets just encode them as they were, ie. blank clause headings. Thanks!

[anermina]

This is applied in #17. Thank you!