Merge branches 'master' and 'mech-rework' of https://github.com/Anuken/Mindustry into mech-rework

# Conflicts:
#	core/assets/sprites/block_colors.png
#	core/assets/sprites/sprites.atlas
#	core/assets/sprites/sprites.png
#	core/assets/sprites/sprites3.png
#	core/assets/sprites/sprites5.png
#	core/src/mindustry/ai/BlockIndexer.java
#	core/src/mindustry/core/World.java
#	core/src/mindustry/entities/traits/Entity.java
#	core/src/mindustry/entities/type/BaseEntity.java
#	core/src/mindustry/entities/type/TileEntity.java
#	core/src/mindustry/world/blocks/defense/MendProjector.java
#	core/src/mindustry/world/blocks/defense/OverdriveProjector.java
#	core/src/mindustry/world/blocks/production/Drill.java
#	gradle.properties

core/src/mindustry/entities/traits/Entity.java

@@ -0,0 +1,51 @@
+package mindustry.entities.traits;
+
+import mindustry.*;
+import mindustry.entities.*;
+
+public interface Entity extends MoveTrait{
+
+    int getID();
+
+    void resetID(int id);
+
+    default void update(){}
+
+    default void removed(){}
+
+    default void added(){}
+
+    default int tileX(){
+        return Vars.world.toTile(getX());
+    }
+
+    default int tileY(){
+        return Vars.world.toTile(getY());
+    }
+
+    EntityGroup targetGroup();
+
+    @SuppressWarnings("unchecked")
+    default void add(){
+        if(targetGroup() != null){
+            targetGroup().add(this);
+        }
+    }
+
+    @SuppressWarnings("unchecked")
+    default void remove(){
+        if(getGroup() != null){
+            getGroup().remove(this);
+        }
+
+        setGroup(null);
+    }
+
+    EntityGroup getGroup();
+
+    void setGroup(EntityGroup group);
+
+    default boolean isAdded(){
+        return getGroup() != null;
+    }
+}