Change Base API to be abstract

sources/ServerRealm/API/Unreal/GameRulesAPI/GameRulesAPIBase.uc

@@ -18,7 +18,8 @@
  * You should have received a copy of the GNU General Public License
  * along with Acedia.  If not, see <https://www.gnu.org/licenses/>.
  */
-class GameRulesAPIBase extends AcediaObject;
+class GameRulesAPIBase extends AcediaObject
+    abstract;
 
 /**
  *  Called when game decides on a player's spawn point. If a `NavigationPoint`

sources/ServerRealm/API/Unreal/InventoryAPI/InventoryAPIBase.uc

@@ -20,7 +20,8 @@
  * along with Acedia.  If not, see <https://www.gnu.org/licenses/>.
  */
 class InventoryAPIBase extends AcediaObject
-    config(AcediaSystem);
+    config(AcediaSystem)
+    abstract;
 
 /**
  *  Describes a single-dual weapons class pair.

sources/ServerRealm/API/Unreal/MutatorsAPI/MutatorAPIBase.uc

@@ -18,7 +18,8 @@
  * You should have received a copy of the GNU General Public License
  * along with Acedia.  If not, see <https://www.gnu.org/licenses/>.
  */
-class MutatorAPIBase extends AcediaObject;
+class MutatorAPIBase extends AcediaObject
+    abstract;
 
 /**
  *      Called whenever mutators (Acedia's mutator) is asked to check whether