Fixes refresh token for new authentications

Although 0505d79ff correctly copied the refresh token from the params
when a user signs in with a refresh token, it also overwrote the *real*
refresh token that YouTube gives back for new authentications (done with
an authorization code).
Include yt-analytics.readonly in test scopes

The two test YouTube accounts used to run tests on Travis CI now
also include the yt-analytics.readonly scope
Move :owner_name from ContentOwner to Account

In this way, it is possible to call account.owner_name and identify
whether any account is a partnered content owner or not.
Let non-partnered channels retrieve five reports

Five reports (views, comments, likes, dislikes, shares) can now be retrieved
by channels without having to be authenticated as a content owner.

Notice that the channel’s account must have authorized the
yt-analytics.readonly scope to obtain the reports.
Merge branch 'metrics-for-non-content-owners'