ByteUnit & Hard Drive Space Check

Added: ByteUnit for conversion between different byte "stages" (e.g.
kilobyte, megabyte etc.).
Added: The hard drive now throws an OutOfSpaceException whenever you
change the content to one which the drive can't handle or you move the
file to another drive which can't handle the new bytes.
ProfileSerializerTest Cleanup

Removed: Some old file serialization stuff which I forgot to remove from
the test.