perf: Tighten useless information from rendered structures

[phorward]

Currently, a bone that is rendered looks like this:

"structure": {
  ...
  "active": {
    "descr": "Aktiv",
    "type": "select",
    "required": true,
    "params": {},
    "visible": true,
    "readonly": false,
    "unique": false,
    "languages": null,
    "emptyvalue": null,
    "indexed": true,
    "multiple": false,
    "values": {
      "0": "Nein",
      "1": "Ja"
    },
    "sortindex": 8,
  }
  ...
}

but it can also be defined as below, when assuming some defaults for the given attributes:

"structure": {
  ...
  "active": {
    "descr": "Aktiv",
    "type": "select",
    "required": true,
    "indexed": true,
    "values": {
      "0": "Nein",
      "1": "Ja"
    },
    "sortindex": 8,
  }
  ...
}

This omits attributes like visible: true or readonly: false, as they need only be set when explicitly required, so a visible: false-bone is attributes as so, same as a readonly: true bone.

It tightens the amount of data being sent to the client without loosing any information. We should discuss about this.

[phorward]

#1203 relates to this.