JSON export bugfixes

[Floppy]

I was trying to debug my 3MF exporter using to_json, and found a few bugs that tripped it up. These changes fix those, so that running to_json on a loaded male02.obj file now works. No extra tests added, just a few quick tactical fixes that seem fairly obvious.

Incidentally, to_json in other contexts would normally produce a string, whereas this creates a hash which then needs JSON.generate() calling on it. Maybe something to reconsider down the line, what the "correct" output from to_json should be.

[Floppy]

The test failure here is because there is an extra level of object in the children array now. Rather than just containing objects, it contains complete to_json output from the child objects, including a metadata section. I'll update the code to pass, but I'm wondering, what should this be outputting? Should the metadata be in there? Or should it just be the contents of the "object" part of the child?

[Floppy]

Trying to phrase my question better. Which is the correct output?

{
  :metadata=>{
    :version=>4.3, 
    :type=>"Object", 
    :generator=>"ObjectExporter"
  }, 
  :object=>{
    :uuid=>"c52c90fd-8f3c-43ec-967f-4714b6a4a482", 
    :type=>"Object3D", 
    :matrix=>[1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0], 
    :children=>[
      {
        :uuid=>"cedd4b1e-e86d-4eb2-8591-314c5cec2e2a", 
        :type=>"Object3D", 
        :matrix=>[1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0]
      }
    ]
  }
}

or

{
  :metadata=>{
    :version=>4.3, 
    :type=>"Object", 
    :generator=>"ObjectExporter"
  }, 
  :object=>{
    :uuid=>"c52c90fd-8f3c-43ec-967f-4714b6a4a482", 
    :type=>"Object3D", 
    :matrix=>[1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0],
    :children=>[
      {
        :metadata=>{
          :version=>4.3, 
          :type=>"Object", 
          :generator=>"ObjectExporter"
        }, 
        :object=>{
          :uuid=>"cedd4b1e-e86d-4eb2-8591-314c5cec2e2a", 
          :type=>"Object3D", 
          :matrix=>[1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0]
        }
      }
    ]
  }
}

[danini-the-panini]

The first one, we don't need the metadata on every child object

[Floppy]

Great, thanks, I'll update the code :)