Text object rendering

[even1024]

Implement rendering of text nodes loaded from KET-files. Current format is:

    "nodes": [
        {
            "type": "text",
            "data": {
                "content": "{\"blocks\":[{\"key\":\"9gsf\",\"text\":\"test 123\",\"type\":\"unstyled\",\"depth\":0,\"inlineStyleRanges\":[],\"entityRanges\":[],\"data\":{}}],\"entityMap\":{}}",
                "position": {
                    "x": 5.6000000000000005,
                    "y": 5.45,
                    "z": 0
                }
            }
        }

[even1024]

Fixed in 1.8