add links for events/conferences/submitters

What do you say we add some links in our conference dashboard so that we not only see the top submitters' names, but we are also able to navigate and see the rest of their info?
at first you could write it in with `inject`

```ruby
Conference.all.inject do |submissions, conference|
  submissions << self.proposals(c) unless self.proposals(c).empty? 
end
```

at second, why we cannot collect this info via ActiveRecord?
Like user can has many proposals somehow via plain rails api `has_many` or `has_many :through`
and then we can hook up on that and get submissions from that. How about that?

Because in general, if you can achieve stuff via AR, you should. As it is way more performant and lean.