fixed getUTCTimeStamp() milliseconds format
ref. http://fixwiki.org/fixwiki/UTCTimestampDataType
added clearing member fields to fieldmap
ref. http://www.fixtradingcommunity.org/pg/structure/tech-specs/additional-resources/user-defined-fields/user-defined-fields-tab-3
fixed `Message.getRepeating()` error when given an array for argument 2.
it was caused by `this` scope.
added some broker's defined fields