add categories to the metadata overview

[bakhshir]

It would be very useful to have another column in the project metadata overview, which displays a number of categories for a given project. This way I could, for example, check if I added calls and infra information to the project pages.

[ewan-escience]

How would you like to see categories counted? Should e.g. only assigned structural leaf nodes be counted (nodes that don't have any children) or assigned incidental leaf nodes (nodes that do have children but of which no child is assigned to the project) or the size of the whole tree or something else?

[bakhshir]

Let's try the leaf nodes count. In this way, it would be easier to spot the problem - missing meta data on the categories if there the count is too low.