corrected check to allow segNumBits to be 53 bits instead of 52
corrected call to Handle.isValidBlockNum to pass FSMNaive's props object
* teaked check for optional offset parameter
* uncommented out validateCRC16 and validateCRC32"
* IMPORTANT: always >>>0 the result of a crc32() call to gurantee the number
  will be treated as a positive integer; otherwise it will be treated as a
  _signed_ 32bit integer.
* teaked check for optional offset parameter
* uncommented out validateCRC16 and validateCRC32"
* changed 'number of segments' entry in the BlockFile metadata block to be a
  DoubleBE (rather that a UInt32BE) so that it can encode segment numbers larger
  than 32bits; as would be in most cases where numHandleBits == 64.
* changed BlockFile metadata buffer's crc to CRC32 from CRC16, and renamed
  the MD_MAP entry 'crc32 value' from 'crc16 value'.
* added, but don't use, the 'metaProps' entry in the MD_MAP.
added "use strict"; at beginning of each file
added isValidMetaProps and assertValidMetaProps class methods