Invert inhibitAdvancedLogin default, implement alternate server cleanup.

Fixes #466, #469.

When the app is using the default config.js settings, inhibitAdvancedLogin will now be true. When you start the app having already had an alternate server setting, you will be prompted to change the setting. You can refuse, but you will continue to be prompted at app start until you accept the change. (Go with the flow...)

I put the setting check just before resurrection of the remembered account. The spiderOakApp.checkAlternateServerAllowed() function call can be easily relocated, if that's not the best place.