switched from 'RandomAccessFile' and 'FileOutputStream' to 'FileChannel'
created the 'ExtendedFileChannel' class for easier access to the 'FileChannel'
storing file offsets as 'long' instead of 'int' to allow files larger than 2 GB
added an 'EntryIterator' that iterates over key,value pairs
using trove maps to map the keys to the value offsets
changed the logger output of 'DMap' and 'CachingHashMap' from 'info' to 'debug'