Qt: Add bits display support to the byte view.

Add todo items for showing and hiding the offset, hex/bits, and
ASCII/EBCDIC sections and adding UTF-8 support.

Change-Id: Ia40faf3f939ef1a8fca6fac827057bd89045482a
Reviewed-on: https://code.wireshark.org/review/4949
Reviewed-by: Gerald Combs <gerald@wireshark.org>