Prompt user for credentials on upload if needed

[PurpleGuitar]

From Chuck: ...would it be possible for BTTwriter to prompt you for credentials? That is, I logged in locally and when to upload a repo and instead of being challenged for credentials, it just responded with a message of "Cannot upload without connecting to a server account." I think that's a change from the old tS days.
​
Craig's response: Hi Chuck Liesch, thanks for your feedback. That's standard tS behavior; if you're logged in locally you have to "log out" before you can connect to a server and upload. It's a good idea to help the user jump right to that though! I'll add it to the backlog.