Big changes to placement across multiple monitors.
Add a Primary option for which monitor to place new windows on. Make "Active" the default instead of "Any", which is just totally crazy.
When a window is being placed in the FOREGROUND, use a monitor chosen in
the following order:
1. same monitor as parent
2. primary monitor if placement=PRIMARY
active monitor if placement=ACTIVE
pointer monitor if placement=MOUSE
3. primary monitor
4. other monitors where the window has group members on the same desktop
5. other monitors where the window has group members on other desktops
6. other monitors
When a window is being placed in the BACKGROUND, use a monitor chosen in the
following order:
1. same monitor as parent
2. other monitors where the window has group members on the same desktop
2a. primary monitor in this set
2b. other monitors in this set
3. other monitors where the window has group members on other desktops
3a. primary monitor in this set
3b. other monitors in this set
4. other monitors
4a. primary monitor in this set
4b. other monitors in this set
Decide to focus the new window before placing it, so we know if it will be
placed in the foreground or background.
Always choose a single monitor, then place on it, rather than possibly moving
to a "backup" monitor. Unpredictable monitor placement is horrible.