Improve remembering of logged in user

[rhiaro]

Remember profile properties and storage URI etc between page reloads.

Sometimes the server still considers a user authenticated even between page reloads due to the browser session persisting (or something) but dokieli forgets everything until the WebID is typed again. So there are some operations you can do whilst appearing not logged in, but you're actually authenticated so they work (without even a cert popup). If we do a HEAD to check the user is logged in at the start - if the user is authenticated, it'll be great and silently populate all the data we need, but if they're not it will trigger annoying cert popups.

Maybe this is something we can solve with localstorage only... the user authenticating again (eg. as someone else) would reset the localstorage, so it should be reliable? But if the the server decides to timeout the authentication session, I don't know if there's a way to reliably update local storage.