project-related roadmap filtering/grouping: project group boxes on|off

[falkb]

At present, each project groups its milestones into boxes. One should be able to turn that grouping off while keeping the ability to filter some projects out for displaying

[falkb]

Actually, this is already possible now switching the plugin component "SmpRoadmapProject — Groups milestones by 'Project'" globally on/off:

[components]
simplemultiproject.roadmap.smproadmapproject = disabled

But we want it by checkbox on the roadmap page. And then all milestones and maybe versions should be chronologically sorted, independently from project. The latter might be the most tricky thing of this ticket.

[Cinc-th]

In 14993:

• Removed private template for creating roadmap page. Instead the version information is added to the default page.
• Replaced roadmap grouping component by a new one using Genshi template for grouping.
• Allow enabling/disabling of grouping.

Note that filtering by project is currently somewhat broken when grouping by project.

Fixes #10087

Refs #12031 esp. comment:9:ticket:12031

[Cinc-th]

Ticket #12556 was created for the filtering issue.