Use the Altis colour scheme for the admin bar on the front end

For [reasons that aren't entirely convincing](https://core.trac.wordpress.org/ticket/51674), WordPress core doesn't use the chosen colour scheme in your profile on the front end. This means on an Altis site you see the dark blue admin toolbar in the admin area, but the standard dark grey one on the front end. Notably the hover styles are very different.

Perhaps on Altis we should use the chosen colour scheme for the front end toolbar too.