Tweaked dig site code for Subterranean Enigma.

Fixed policy localization.
Added a new random colony event, The Subterranean Enigma.

Removed cleanup event.

Fixed wrong targeting.

Added the goto button that was missing to jump to the new system.

Forgot some files.

Added a new event chain: Celestial Disturbance.
Changed how the Alshigans event chain work by spawning new systems instead of finding a suitable one.
Deactivated the Alshigans event chain for multiplayer and added a monthly cleanup event for those who are stuck in it.

Added safeguards to some triggers to avoid a desync issue.
This will fix the technologies and buildings of Strange Worlds planets unlocking before they're colonized.

Updated required version to the new launcher syntax.

Made some tweaks and fixes to the Roots event chain and decisions.
Fixed a wrong scope in Tower City rewards.
Updated Planetary Diversity compatibility.