Add dimension property (2D/3D)

3D information was not reported, and could be integrated in the title.

    For: Coraline.3D.1080p.BluRay.x264-FlexGet.nfo
    GuessIt found: {
        [0.80] "releaseGroup": "FlexGet",
        [0.80] "videoCodec": "h264",
        [1.00] "container": "nfo",
        [1.00] "screenSize": "1080p",
        [1.00] "format": "BluRay",
        [0.60] "title": "Coraline 3D",
        [1.00] "type": "movieinfo"
    }
    
After the fix:

    For: Coraline.3D.1080p.BluRay.x264-FlexGet.nfo
    GuessIt found: {
        [0.80] "videoCodec": "h264",
        [1.00] "container": "nfo",
        [1.00] "format": "BluRay",
        [0.60] "title": "Coraline",
        [0.80] "releaseGroup": "FlexGet",
        [1.00] "screenSize": "1080p",
        [1.00] "type": "movieinfo",
        [1.00] "dimension": "3D"
    }