Save restore position when minimized

[HebaruSan]

Problem

If you:

1. Open CKAN with the tray icon enabled
2. Minimize it
3. Right click the tray icon
4. Exit

... then the following is saved to GUIConfig.xml:

And the next time CKAN runs, its window will not appear.

Cause

Apparently Windows moves minimized windows to (-32000,-32000).

https://stackoverflow.com/questions/1478765/location-coordinates-on-computer-showing-x-32000-y-32000

So when we exit and save the Location property while minimized, we're saving that value.

Changes

Now we ignore Location if the window state isn't normal (i.e., we're minimized or maximized), and instead we check RestoreBounds.Location, which is where the window's former location to which it will be returned lives. This mirrors how we handle the window size on the next line of code (though in that case the problem was with maximization).

Fixes #2717.

[DasSkelett]

Works as intended

[HebaruSan]

I'm thinking it should also recover from the issue once the file already has -32000 in it. Please hold off on merging till that's added.

[HebaruSan]

Updated to default to center of screen when the saved position isn't on any of the known screens.