Edit community details with editor

Edit everything with mercury instead of current form. All these are stored in community customizations (community customization is not yet) and edited on that language what is chosen in the UI at the moment of editing.
- slogan (edit UI)
- description (edit UI)
- Community name (edit UI)
- Store community name in community customizations and use it from there
- Add option to easily check how homepage looks to non-logged-in users