Map localization: Remove duplicate old generation overlays

For those languages where new overlays are available, we don't need
to keep the old ones.

[ci skip]
Remove all old style bigmap overlays but the titlescreen

Without the corresponding maps, the overlays are completely unnecessary.

The titlescreen is preserved for UMC use - all other cases are from
campaigns and aren't guaranteed to be included with the game.

[ci skip]
German translation: Minor progress on EI

Furthermore, minor changes to the German HttT and TRoW translations to match the map overlays.

[ci skip]
German translation: Map overlays

Full set of the mainline campaign map overlays.

[ci skip]
Update l10n-track

As per AI0867's request, the deletions of all old map overlays and the
addition of new ones for the German translation now are registered in
l10n-track.

[ci skip]