[PATCH] Automatic camera control for observers/replays

[elexis]

It would be nice if there was an option for observers to automatically control the camera without user interaction.

This can be accomplished by just focusing the camera on placed foundation and following the entities that received a command.

There might be a military and economic option, so that the viewer could restrict the camera to interesting events.

Requires the change-perspective tool for observers: #3168.