The account manager now uses a stack to switch between a single editor instance
and the list of accounts. The save button from the editor got moved next to the
new back button, but we should probably prompt or throw up an info box when the
user starts making changes or prompt before moving back.

Also, the app.edit-account action now will lose any changes to an account that
is currently being edited, which we should disallow from happening in the future
as well.

Opened the account manager and selected accounts and moved backed and saved accounts and made sure everything there worked.

Opened the account editor from a connection error notification and verified that opened properly as well.