Byte frequency profiler

Getting a byte frequency profile is useful to determine if the session data:

1. is ASCII data (in which case case-insensitive searches can be appropriate) or not
2. has Windows/DOS (`\r\n`) or Unix (`\n`) newlines
3. has null bytes
4. various ratios (e.g., whitespace/punctuation to characters, ASCII to non-ASCII, newlines to total bytes)

