Allow setting "always using tab-page instead of windows"

I like using the tab-page very much, could you please adding config options such like "always using tab-page" or "always open new repo in new tab-page" or "force using single window“。

Now every time I restart source tree, every repo I opened opening in new window, and I have to drag them into one. That makes me sad. I think this option won't heart other users who like using in muti-windows, and not difficult to implement.

Thanks very much!