Discover the datasources contained in the datastore
    corresponding to the OGR string ogr_str, return an
    array of {name,type, hash}

def discover_datasources(datastore_str):
    """ Discover the datasources contained in the datastore
    corresponding to the OGR string ogr_str, return an
    array of {name,type, hash}"""
    
    datastore = DataStore(datastore_str)
    datasources=[]
    for ds in datastore.get_datasources():
        datasources.append({'text':ds.name, 'type':ds.type, 'id':ds.getHash(), 'leaf': True})
    return datasources