finished JSON for structure attributes

MSG
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The JSON for dynamically building tables (representing structure attributes) is completed. This makes for more extensive tables in the omnibox (in point-mode, after having clicked on a work of kunst). The JSON now also provides a default value, to be displayed when a real value is not present in the database. 

TODO
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- [x] Use Freddy's Excel to change the JSON used for building tables at runtime.
- [ ] Update the cardattributes template to show the default value if no real value was found (must be a distinct color, e.g. grey-ish for defaults a.o.t. black for real values)