Various UI grievances to be fixed

[pudo]

ported from alephdata/aleph#142

• Replace "Possible duplicates" section in entity view with something "less confusing" (user quote).
• Make it easier to find your personal collections from current investigations.
• Inside collections, rework the whole user experience (needs a UX person)
• Separate entity links into different categories and show these as separate pagers on entity profiles ("subsidiaries", "shareholders", "family", "directors").
• Allow users to delete documents via the UI (API endpoint exists).