TZX updates - mostly for easier JSON parsing

[mrcook]

While trying to test a bunch of tape images (over 21K files) I encountered some issues. Parsing the JSON output was also being a bit annoying, so I made changes to make that easier.

• quite a few tapes utilise unofficial TAP block types, which don't trouble the emulators, so I've added support for these.
• all of the data fields have been changed to be an array of U8 values.
• I've wrapped the TAP blocks in a FieldStruct so the JSON can be more easily parsed.
• the Hardware block field names were too cryptic, so I've renamed them.

[wader]

Ok to merge?

[mrcook]

Ok to merge?

Yes, please do! And again, thanks Mattias!