Support for JSON5

[gregsdennis]

This would include support for things like BSON and comments.

Ideally, I'd like to update the parser system to allow for injection of sub-parsers from external code. This would mean that the additional parsers could live in a secondary library, leaving Manatee.Json to implement "pure" JSON.

[gregsdennis]

Will need to support some sort of analog to WPF's attached properties to store the non-standard information contained in the JSON. Otherwise, converting back to a string will not result in the same string as the input.

[gregsdennis]

See nonstandard branch.

[gregsdennis]

Having difficulties with new parsing logic and trying to implement a comment parser. Identifying the comments is easy, but I'm having to rewrite some of the existing logic to support it, and supporting comments anywhere (e.g. before key, after key, after colon, after value) is proving difficult.

[gregsdennis]

I think it would be better to simply support JSON5. Still want to do this in a separate library, sort of as a plug-in.