Currently the various `other/palisades_*` files inherit from various wall templates. This patch introduces a new `template_defensive_palisade.xml` to remove duplication in the palisade files.
Minor tweaks:
* standardized palisade armour
* default capture points to 500 (same as tower), rather than city walls' 1200
* removed stone costs and stone loot
* added minor wood costs and default 10 wood loot
* village phase requirement