[maps] Fix entities placed outside of the passable map area on wild_lake.js and caledonia_meadows.js

Reported by Gurken Khan:
https://wildfiregames.com/forum/topic/82754-alpha-26-pre-releaserelease-candidate-build-testing/page/4/#comment-503140

Fix:

rename "actor" to "entity" as that makes it clearer what it actually is and use placeEntityPassable() to assure that nothing is placed outside of the map.

also:
include https://code.wildfiregames.com/D2149 patch by @FeXoR
reduce the amount of entities placed on wild_lake. It looked extremely crowded.

accepted by: @lyv

Differential revision: https://code.wildfiregames.com/D4699