function addMetaSchema(schema, key, skipValidation) {
    addSchema(schema, key, skipValidation, true);
  }
Add schema that will be used to validate other schemas
options in META_IGNORE_OPTIONS are alway set to false
@param {Object} schema schema object
@param {String} key optional schema key
@param {Boolean} skipValidation true to skip schema validation, can be used to override validateSchema option for meta-schema