Choose game instance if default is locked

[HebaruSan]

Problem

If you have multiple game instances, you've selected one as the default instance, and you open that instance in CKAN, then opening another copy of CKAN will cause it to print an error about the instance being locked and quit.

However, if you have no default instance, then in the same flow you will be prompted to choose an instance. The user shouldn't lose options because they've selected a default instance.

Changes

Now if the default instance is locked by another process but there are other unlocked instances, the Manage Game Instances popup appears. Instances that have a CKAN/registry.locked file will have "(LOCKED)" appended to their names, so you can tell which ones are open in other instances of CKAN:

Also the Linux man page's documentation for the ckan ksp subcommand is updated to the current ckan instance naming.

Fixes #3375.

@CodeLeopard, there should be a test build under the Checks tab shortly after this is submitted, if you wouldn't mind giving it a try.

[CodeLeopard]

I tested it and it works for the most part, but I did ran into a problem:

If I select a locked instance it just re-opens the selection dialog, in an ideal situation it would show the "Instance is locked" dialog at this point (but then still show the selection dialog again).

If I then select the locked instance again (after the selector re-appears) the full GUI starts up and immediately throws an exception: RegisteryInUseKraken. If I select continue the GUI has no window title and it does not populate the mods list.

[CodeLeopard]

Okay I just tested the new version and it works properly in the startup case.

However I did discover another issue that occurs when switching between instances (not opening a new one):
In the full GUI, go to: file -> manage instances and select a locked instance, it throws RegisteryInUseKraken.

The 'instance is locked' error not appearing on the correct screen did happen to me, but it does put that message on top so I saw it immediately, I don't think it's a big problem.

[HebaruSan]

However I did discover another issue that occurs when switching between instances (not opening a new one):
In the full GUI, go to: file -> manage instances and select a locked instance, it throws RegisteryInUseKraken.

OK, now the GUI catches that exception, displays an error for it, and goes back to working with the original instance. There's a little delay because technically just the attempt to open the other instance invalidates certain things and we need to make sure everything is set up properly again.

https://github.com/KSP-CKAN/CKAN/suites/2848264095/artifacts/63574915

[DasSkelett]

Just pushed the German translation, and also renamed ManageGameInstancesInvalid/ManageGameInstancesLocked -> ManageGameInstancesNameColumnInvalid/ManageGameInstancesNameColumnLocked to differentiate them a bit from ManageGameInstancesNotValid.
The new name is admittedly not the best, but I couldn't think of a better one.

[DasSkelett]

Yup, should be good now. Nice enhancement, thanks for the suggestion @CodeLeopard!