addon catalog (CatalogFiltered): no installed addons

[Ivshti]

Using CatalogFiltered and addonCatalogs for addons is great, but it has a flaw: there are no installed addons in the catalog

this can be solved:

• at a UI level, add another route /installed which just displays ctx.content.addons with some filtering
• by wrapping CatalogFiltered and adding installed by splitting the Load action into Installed(type) or Catalog(resource_ref); this has two extra advantages:
  • allows to structure the navigation conveniently at a model level (we can choose between catalog -> type or type -> catalog)
  • different Load action for addons; otherwise we have to wire msgs in the app in such a way that only model.discover or only model.addons will receive a certain Load
  • we can also implement addon search, see in-memory search for various models #93
• by creating a fake addon

[nklhtv]

its done on the UI level before core