Convert users to sign up

[hexylena]

I think we're doing a poor job of converting anonymous users into signups. This presents as a common problem in training of "why isn't X available" or "where is my history button" which we have to explain often.

I think we should do a couple things:

• an always-on banner with "Some features will not available until you register. Click here to register. Thank you for trying Galaxy!"
• Present more visual cues in the GUI for options that are only available when logged in #10418
• We should re-add the disabled buttons but grey them out
  • history switch
  • workflows
  • user menu
  • generally make it look 100% like the logged in process (with the addition of the banner)
• On hover there should be a popup "This feature is only available for registered users"
• On click of those (visually) disabled buttons, redirect them to the registration page.

See slack's example of "Show the feature they want + convert"

xref #5898 but orthogonal. xref #11374 which is part of the reason this came up