Retain Navigation State after Login

[grolu]

We keep most of the navigation state in the URL (including pages and tabs, but currently excluding dialogs and form data). This way, it is possible to send e.g. links, that point to a specific cluster of the gardener Dashboard.
However, if the user that opens the URL is currently not logged in to the dashboard, he is redirected to the login page and looses navigation information: After successful authentication, the user is redirected to the start page (which is - for most cases - the cluster overview).
We need to improve here, especially as this issue will increase after #328 gets merged. This PR will significantly reduce the token lifetime and lead to more authentication and redirects to the start page.
Moreover, we should discuss if we want to include more information (about open dialogs, unsent form input, etc.) into the URL, or store it in local browser store.