'Create a database of VO services from a JSON file.
Example JSON format for Cone Search::
"__version__": 1,
"catalogs" : {
"My Cone Search": {
"capabilityClass": "ConeSearch",
"title": "My Cone Search",
"url": "http://foo/cgi-bin/search?CAT=bar&",
"Another Cone Search": {
Parameters
filename : str
JSON file.
kwargs : dict
Keywords accepted by
:func:`~astropy.utils.data.get_readable_fileobj`.
Returns
db : `VOSDatabase`
Database from given file.'

@classmethod
def from_json(cls, filename, **kwargs):

    with get_readable_fileobj(filename, **kwargs) as fd:
        tree = json.load(fd)
    return cls(tree)
