Add key shortcut to toggle between top view and previous camera perspective.

[Radagast]

When placing walls in Atlas, you have to check if wall segments are aligned properly with connected towers or other segments.

With only one perspective this is a very tedious guesswork.

It would be nice to be able to switch into top view for a short moment using a key shortcut.

When pressing the same key shortcut again, the camera view could jump back to the previous perspective.

This way the following workflow was possible:

• Add wall segment.
• Rotate.
• Roughly align in perspective view.
• Switch to top view to check alignment + if there are any entity collisions.
• Correct alignment in top view.
• Switch back to perspective view to add or copy + paste more elements or to check entity collisions.