Better branding and restructuring the navbar

[ml-evs]

Currently deployments can configure the window title, and logo header for the main page. Some other things we should consider:

• refactor global navbar for usability and have spots for logos and an app title e.g., "The X Group Datalab", with a customisable colour for this global bar.
• this config itself could be moved into the server config, i.e., the app reads from an info endpoint that populates the logos and so on without needing these available at build time (thus it would only need the API URL which can be passed easily without a separate app config file).
• this navbar should also show the current user and better capture the options for login (dynamically from what the server supports).