Add a way to keep unhandled or all Confluence macro parameters, prefixed

There is a need to keep all the macro parameters so there's a chance that stuff that's currently buggy or unsupported can be fixed using post-processing.

We introduce two parameters:

• Kept macro parameter prefix (default value: "confluence_"): when keeping original confluence parameters, use this prefix to name the kept parameters in the converted macro
• Kept macro parameter mode
  • NONE: the default, and the current behavior of dropping all the parameters, and letting macro converters produce their parameters
  • ALL: Keep all the original Confluence parameters, unless their prefixed version conflicts with a parameter that the macro converter defined
  • UNHANDLED, same, but only keep the parameters that have not been handled / used by the macro converter and that the macro converter hasn't explicitly marked as handled.