Can tags be non exclusive?

[chevdor]

If I want to open a discussion regarding, say Council and Treasury.
Which one should I pick? Council? or Treasury?

Can I pick both? Or more as appropriate?

[Tbaut]

That's not possible easily. We should see it as a category, rather than a tag. We should probably remove these for discussions, and actually create tags, that could be more useful.

[Tbaut]

from @rrtti in #794

I'd like to use the categories when submitting a new post as a way to filter different discussions on my dashboard. If I click on the category I should be able to see all posts included on this category. Furthermore, if I filter discussions using two or more categories, these discussions should appear on my dashboard.

Make categories flexible: I want to be able to choose more than one category when posting (i,e: treasury + council), this could allow crossed-topic categories as a new filter.
Make "Filter by category" possible on dashboard: I want to be able to click on tags and see crossed-topic discussions.