[gameplay] Make siege engines uncapturable

Siege engines are faster to destroy than to capture. As such, capture as
a default is annoying, since it's not the best tactical choice.
Unfortunately, fixing this for now means removing "Capturable" from
siege engines.

Rams/Siege towers retain 50 Pierce Armour, others get 25.

Patch by: Nescio
Differential Revision: https://code.wildfiregames.com/D2493
This was SVN commit r24685.

binaries/data/mods/public/simulation/templates/template_unit_siege.xml

@@ -1,10 +1,5 @@
 <?xml version="1.0" encoding="utf-8"?>
 <Entity parent="template_unit">
-  <Capturable>
-    <CapturePoints>500</CapturePoints>
-    <RegenRate>10</RegenRate>
-    <GarrisonRegenRate>10</GarrisonRegenRate>
-  </Capturable>
   <Cost>
     <Population>3</Population>
   </Cost>
@@ -33,7 +28,7 @@
     <Entity>
       <Damage>
         <Hack>1</Hack>
-        <Pierce>50</Pierce>
+        <Pierce>25</Pierce>
         <Crush>5</Crush>
       </Damage>
     </Entity>

binaries/data/mods/public/simulation/templates/template_unit_siege_boltshooter.xml

@@ -31,9 +31,6 @@
       </Splash>
     </Ranged>
   </Attack>
-  <Capturable>
-    <RegenRate>20</RegenRate>
-  </Capturable>
   <Cost>
     <BuildTime>20</BuildTime>
     <Resources>

binaries/data/mods/public/simulation/templates/template_unit_siege_ram.xml

@@ -15,7 +15,6 @@
       <RestrictedClasses datatype="tokens">Field Organic</RestrictedClasses>
     </Melee>
   </Attack>
-  <Capturable disable=""/>
   <Cost>
     <BuildTime>30</BuildTime>
     <Resources>
@@ -44,6 +43,13 @@
     <wood>60</wood>
     <metal>30</metal>
   </Loot>
+  <Resistance>
+    <Entity>
+      <Damage>
+        <Pierce>50</Pierce>
+      </Damage>
+    </Entity>
+  </Resistance>
   <Sound>
     <SoundGroups>
       <select>attack/siege/siege_select.xml</select>

binaries/data/mods/public/simulation/templates/template_unit_siege_stonethrower.xml

@@ -25,9 +25,6 @@
       <PreferredClasses datatype="tokens">Structure</PreferredClasses>
     </Ranged>
   </Attack>
-  <Capturable>
-    <RegenRate>20</RegenRate>
-  </Capturable>
   <Cost>
     <BuildTime>25</BuildTime>
     <Resources>

binaries/data/mods/public/simulation/templates/template_unit_siege_tower.xml

@@ -88,6 +88,13 @@
   <StatusBars>
     <HeightOffset>12.0</HeightOffset>
   </StatusBars>
+  <Resistance>
+    <Entity>
+      <Damage>
+        <Pierce>50</Pierce>
+      </Damage>
+    </Entity>
+  </Resistance>
   <UnitMotion>
     <WalkSpeed op="mul">0.7</WalkSpeed>
   </UnitMotion>