Get max extent CRS from QGIS API.

[wlorenzetti]

Closes: #429

[wlorenzetti]

@volterra79 I just add a new api to get information about CRS, i.e.:

/crs/3003

return

{
    "result": true,
    "data": {
        "epsg": 3003,
        "proj4": "+proj=tmerc +lat_0=0 +lon_0=9 +k=0.9996 +x_0=1500000 +y_0=0 +ellps=intl +towgs84=-104.1,-49.1,-9.9,0.971,-2.917,0.714,-11.68 +units=m +no_defs",
        "geographic": false,
        "axisinverted": false,
        "extent": [
            1226046.6820902952,
            4047095.260762165,
            1727931.8998958569,
            5214000.012210975
        ]
    }
}

[volterra79]

@wlorenzetti thanks

[wlorenzetti]

@volterra79 tell me when you want I merge it on dev.

[volterra79]

@wlorenzetti you can merge it. Thanks