Restyle Accounts Elsewhere section.

Accounts with avatars, and the new Disconnect button, still need to be looked at.
Markup and styles were copied over from the coinbase repo.
Re-used an existing colour variable instead of making a new one that was used.
Cleaned up Bitcoin account presentation
Cleaned up avatar + username presentation
Shorten right positon of Disconnect button
Accounts are full-width in small-screen and tablet sizes
Adjustments to Balanced Payments section
Clean up copy in unconnected case
Harmonize Balanced copy w/ the rest

Balanced is implemented without the account-row macro, so it requires a
bit of manual tweaking.
Merge pull request #2142 from gittip/connected-accounts-restyle

Connected accounts restyle