This patch (requested by @bb in D1791) adds some attributes to the `template_structure_military.xml` template, to reduce the amount of duplication in its children:
* <BuildRestrictions/Category>Military
* <GarrisonHolder>
* <Sound>
* <TerritoryInfluence>
Furthermore, it removes footprint, rubble, obstruction, and visual actors from the generic Barracks template, because these belong in civ specific templates.