Issues #507 and #514 - advanced login link and no server prompt

- Removes initial server prompt
- Adds "advanced login settings" link (calls the `setInitialServer` function from the removed prompt)
- Adds a "Learn more..." link to the login screen when the preliminary screen is disabled
Tweaked to get the correct value for `s("SpiderOak")`
Merge pull request #515 from SpiderOak/issues-507-and-514-adv-login-link-and-initial-server

Issues 507 and 514 adv login link and initial server