Add fields for basic auth

[ResamVi]

Solves #957

This adds a field auth to the feedreader module:
For private rss feeds returning a 401 it attempts basic auth
by cycling through the auth list This was changed (see comment below)

E.g.:

feedreader:
  enabled: true
  feeds:
  - http://localhost:3000/feed/rss.xml
  auth:
  - ["user", "password"]
  - ["john doe", "supersecret"]
  feedLimit: 10
  position:
    top: 1
    left: 1
    width: 2
    height: 1
  refreshInterval: 14400

I've added a test but it's in the app folder because otherwise it would cause an import cycle.

This upgrades the gofeed dependency to a more recent commit (three days ago, that's some lucky timing) where basic authentication is implemented

[Seanstoppable]

I'm concerned about the strategy of cycling through the auth list, as you are effectively sending your credentials to a bunch of sites.
Per @senorprogrammer's comment on the issue, we probably want a more robust struct of data if we want to support this, so there is a 1:1 mapping of credentials to url.

[ResamVi]

OK, I see. 👍 I'll change it to a proper mapping

[ResamVi]

The new structure looks like this now. Of course it's still backwards compatible with the old list structure

feedreader:
  enabled: true
  feeds:
    http://localhost:3000/feed/rss.xml:
      username: john doe
      password: supersecret
    http://localhost:3001:
      username: anna
      password:
  feedLimit: 10
  position:
    top: 1
    left: 1
    width: 2
    height: 1
  refreshInterval: 14400

[senorprogrammer]

Looks great 💯