Latest changes for BinJSON support.

- Fix URLLoader to allow for optional secondary file matching (after extension matches).
- Implemented wildcard file matching for json files in BinJSON to support file match sets in settings.json.
- Implemented missing Indexer setters in BinJSON.
- Fixed some conversion issues.
- Made sure the JSON replacement keys all start with a '$' so they're easy to identify.
- Reverted the use of WeakKeyCollection in JSON as it wasn't working.  Need to find a better solution.