The recent introduction of the artillery and bolt towers messed up some things, because the new templates were carelessly copied from the scout/stone/defense tower templates. This patch tries to bring some order and does the following:
* Classes:
* The `Defensive` class is made visible (cf. `Civic`, `Economic`, `Military`).
* The `Fortress` class is made visible (because of build restrictions).
* The `Tower `class defined in `template_structure_defensive_tower.xml` is now visible.
* The unused `GarrisonTower `class is removed.
* The `DefenseTower` class is deprecated in favour of one unique class in each of the `*_tower.xml` children templates:
* `*_artillery.xml` → `ArtilleryTower`
* `*_bolt.xml` → `BoltTower`
* `*_sentry.xml` → `SentryTower`
* `*_stone.xml` → `StoneTower`
* `template_structure_defensive_wall_tower.xml` does not inherit from `*_tower` and therefore has a `WallTower` class instead of a `Tower` class.
* Updated the `Identity.js` file accordingly.
* Updated the Petra AI files accordingly (`DefenseTower` → `Tower`).
* Tower build restrictions are changed to simply `Tower`.
* Technologies:
* `tower_armour.json` affects all towers, but not outposts (unchanged).
* `tower_decay.json` and `tower_vision.json` affect only outposts (unchanged).
* `tower_crenellations.json`, `tower_murderholes.json`, `tower_range.json`, and `tower_watch.json` affect now only the Sentry and Stone towers, instead of all towers. This alters gameplay for the Artillery and Bolt tower, but those shouldn't have been benefitting from arrow tower technologies anyway.
* Standardized the tooltips per the [[ https://trac.wildfiregames.com/wiki/EnglishStyleGuide | style guide ]].
* Updated the <Identity/Tooltip> in the tower templates.
* [EDIT] Inserted <BatchTimeModifier>1.0</BatchTimeModifier> in `template_structure.xml`, where the <ProductionQueue> is defined, and removed the <BatchTimeModifier> from templates that can't train any units.
Checked with `grep -ir -e DefenseTower -e GarrisonTower simulation/*`
Related: D2494, D2495.