Extension properties are not properly ignored

Currently when the php-cmis-client is parsing property definitions, if it receives a property in the type definition that it does not recognize, this causes an exception to be thrown. I noticed this when using php-cmis with a Filenet server that has the "isHidden" extension enabled. Here is a sample of the data returned from the browser binding.

"IndexationId": {
"id": "IndexationId",
"localName": "IndexationId",
"displayName": "Indexation Id",
"queryName": "IndexationId",
"description": "The object ID of the verity collection an object is stored into, or null for objects that were full text indexed prior to the 4.0 release.",
"propertyType": "id",
"cardinality": "single",
"updatability": "readonly",
"inherited": false,
"required": false,
"queryable": true,
"orderable": true,
"openChoice": false,
"isHidden": "false"
},

When php-cmis tries to parse this in the JSONConverter, it ends up in this code.

        array_intersect_key($data, array_fill_keys(JSONConstants::getPropertyTypeKeys(), 1)),
        $propertyDefinition->populate(
            $data,
            [JSONConstants::JSON_PROPERTY_TYPE_RESOLUTION => 'dateTimeResolution']
        );
        $propertyDefinition->setExtensions($this->convertExtension($data, JSONConstants::getPropertyTypeKeys()));

The pouplate() code ends up looking for a setter for isHidden in the determinePropertyAccessFunctionName method and since it cannot find one it throws an exception instead of ignoring it.

        if (empty($accessMethodNames)) {
            throw new AccessException(
                'No "' . $method . '" method(s) can be determined for property ' . $propertyName,
                1422021212
            );
        }

Section 2.1.1.3 of the CMIS specification says the following about unrecognized repository features.

Clients that don’t understand this information SHOULD ignore it.

dkd / php-cmis-client

Extension properties are not properly ignored #67