Multi- to single- to multi-monitor config leaves windows on external monitor

[Ethan Hogue]

Summary:
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When switching between monitor modes, the windows (on the primary desktop) do not follow a logical movement pattern, or one optimized for the user's experience.

Steps to repeat:
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- plug in an external monitor to laptop
- close laptop --> elementary switches to only using external monitor, all windows appear there
- open laptop back up:
     --> WHAT HAPPENS: elementary reactivates the internal monitor as the main monitor, but all windows are still on external
     --> WHAT WAS EXPECTED: windows would jump back to laptop screen

Further reasoning:
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All windows should have "home" monitors, where they want to be unless they are moved by the user. Closing the laptop or unplugging a monitor should make the best of the situation, but retain the information on where a window is supposed to be. For example, if I'm watching a movie on my external monitor -- and that window has focus -- if I close my laptop to only use the external monitor, I don't want the windows from the laptop screen popping up in front of my movie. I also don't want to have to manually drag windows back from the external monitor when I decide to open my laptop again.

[Sascha Heuterer (theanachron)]

Seconded.