Added missing localization.

Loosened the restrictions for spawning the leads for the Shaded Empire.

Removed localization files present in external translations.

Added a missing localization.

Removed the astral rift part of Celestial Disturbance since it had numerous issues.
I will eventually come back to it on a later update.

Code tweaks.

The new policy will default to disabled when starting a new game.

Fixed a number of issues with dig sites.
Added a new policy that automatically cleans up completed dig sites (active by default).
Various bug fixes.

Tweaked dig site code for Subterranean Enigma.

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