Add "sign in" button to DataONE theme
When I log in to the CN portal and then search that CN for packages I can see the user icon with my CILogon DN and "my packages" and "logout" options. This is great! But we should have a button for signing in so users don't have to know where to go. We can start with a url like this:
But instead use an absolute URL for "target" param to direct them back to the MetacatUI page they started from when they have finished authenticating.