[FEATURE] Add a filter plugin that combines category and tag

[sat-hub]

Hello TYPO3GmbH,

this is a new plugin that I created for some project, it combines one Category and one Tag (both optional) into a filter object (interface PostFilter) that is used as query constraints to fetch all matching blogs and listing them.
I created a generic controller action that could handle other kinds of PostFilter implementations, too, the CategoryTag filter being its first implementation.

Fluid template is close to existing layouts and reusing available classes where possible. It renders both categories/tags as horizontal lists, with the current selected one(s) having an "active" class added.

I propose to add this plugin to a 13.1.0 minor feature version. Feel free to ask for things you want to have changed, I'd really like to have this feature added to the official blog extension and not just any other fork!

Kind regards,

Sascha Ternes
Die Medialen GmbH

[sat-hub]

I am currently preparing a rebase on top of the v13 master.

[sat-hub]

Rebase finished - please continue review.