Implement a workaround to AI endless terraform problem.

Fix some event generated leaders not getting leader traits from cybernetic / synthetic / psionic racial traits.
Devouring swarms now have the same interaction with enclaves as fanatic purifiers.

Fix refugees not handling correctly for displacement.
Fix the bug that some observation events can change ringworld to other classes of planet.
Fix the AI admiral given by anomaly.4030 not correctly classified as Synthetic.

Thanks to @Novacat of Paradox forum for pointing out these problems.

Fix a mistake by me in fallen_empire_initializers (regarding fallen empire ringworld).
Further fix to portal holder's function.
Fix Prethoryn auto-purge, so recapture planet from them before purge is done should stop the purge now.

Fix an embarrassing mistake in handling precursor.

Update to support 1.6.0 and 1.6.1 beta

Fix non-functional Enigmatic Decoder.

Fix unexpected dominant species change by having other species gaining psionic trait.
Fix the third tech of horizon signal not showing up.

Further fix to anomaly Projecting Moon
Prethoryn now destroys habitat station when purge is completed, so that it won't colonize the empty habitat and turn it into infested planet.

Fix some errors in ethic and pop faction system.