Also tidy up entry for 4097

Add the classify.xml file to document the client classification
system

Update the dhcp4-srv.xml and dhcp6-srv.xml files to provide a brief
description of the classification system and pointers to the
text in classify.xml

Notable items:
Removed a lot of the classification text from dhcp4.xml and dhcp6.xml
leaving a brief description with a pointer to the main text and some
examples.

Added more examples

This fixes a bug in the TokenOption class which used the hexadecimal
format of the option when comparing with TokenHexString. Note that
TokenHexString is automatically converted to binary format for
evaluation.

Update the v4 and v6 pages to reflect the new classification.
These are shortened versions of the main classification page.

Also update the option description to incude .text and .hex modifiers.