Graph visualization for Red with graphviz

Dot-language syntax is defined here.

• Instead of curly braces square braces are used.

• Red-graphviz syntax uses set-words instead of "attribute =" (e.g. color: 'red]).

• Node ports are mimicked by urls (eg. node:ne) or by get-words, which are attached to strings and tags (e.g. "Are we ready?":e -> <Let's go!>:w). In case of lit-words and numbers, get-word should be separated from the name by space (e.g. 'node :sw).

• There are no commas and semicolons.

• Lit-word may not include dashes.

• usual red words cannot (yet) be used for attribute values (e.g. instead of center: true center: 'true should be used)