Re-arrange CfgVehicles config for buildings and buildables

- All buildables are grouped together now.
- Buildables can be used and found under "DayZ Epoch Buildables" in the editor now.
- Update scope of a few vehicles. Most base classes should be private or at least protected.
- Epoch Loot Container can be found under "DayZ Epoch Crates" in the editor now.

SQF/dayz_code/Configs/CfgVehicles/Graves.hpp

@@ -0,0 +1,16 @@
+class GraveDZE: Land_A_tent {
+	vehicleClass = "DayZ Epoch Buildings";
+	displayName = "Grave DZE";
+	destrType = "DestructNo";
+	model = "\z\addons\dayz_epoch\models\skeleton.p3d";
+	transportMaxMagazines = 80;
+	transportMaxWeapons = 20;
+	transportMaxBackpacks = 1;
+};
+
+class Mass_grave;
+class Mass_grave_DZ: Mass_grave
+{
+	displayName = "Mass Grave W/ Zombies";
+	vehicleClass = "DayZ Epoch Buildings";
+};