[DRAFT] Version 1.0 Update Notification

First draft of update notification for 1.0.

Since we can't control the update notification dialog like we wanted to -- The first item in the new features list is a note that this is our 1.0

Let me know what you want changed.
Oh, also -- I agree with @MarcelGerber's earlier comment here.  Saying "0.45" is confusing because we're not calling it that anywhere else.  How about: "It's official -- Brackets 1.0 is here!"