Added file reading and writing to ArrayBlockSorted.
Added iteration to MapBlock.  Added file reading and writing to MapBlock.
Added MapStringBlock that keys by a string into a variable sized data.
Made AssertMD5 NULL safe.
Converted MapTemplate to extend MapBlock.  Converted MapStringTemplate to extend MapStringBlock.  Renamed Map.GetWithKey to Map.Get.
Allow empty properties in the properties file.