Link rules with Style Guide

[bhirsz]

Robot Framework Style Guide links some of its recommendation with our rules. It may be good idea to enhance our rules documentation with links to Style Guide whenever our rule covers given part of the Style Guide.

[bhirsz]

Implemented in #1307 - some rules may be linked later after rule behaviour change etc. But there is basic setup in place for linking and displaying in our docs.

We now need do the same with formatters (if it makes sense) and cross reference in style guide as well.