Moves some classes to the new container package, and improves some code

src/test/java/net/knarcraft/stargate/BlockLocationTest.java

@@ -2,6 +2,7 @@ package net.knarcraft.stargate;
 
 import be.seeseemelk.mockbukkit.MockBukkit;
 import be.seeseemelk.mockbukkit.WorldMock;
+import net.knarcraft.stargate.container.BlockLocation;
 import org.bukkit.Material;
 import org.junit.After;
 import org.junit.jupiter.api.BeforeEach;

src/test/java/net/knarcraft/stargate/RelativeBlockVectorTest.java

@@ -1,5 +1,6 @@
 package net.knarcraft.stargate;
 
+import net.knarcraft.stargate.container.RelativeBlockVector;
 import org.junit.jupiter.api.Test;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;

src/test/java/net/knarcraft/stargate/portal/GateLayoutTest.java

@@ -2,7 +2,7 @@ package net.knarcraft.stargate.portal;
 
 import be.seeseemelk.mockbukkit.ServerMock;
 import be.seeseemelk.mockbukkit.WorldMock;
-import net.knarcraft.stargate.RelativeBlockVector;
+import net.knarcraft.stargate.container.RelativeBlockVector;
 import net.knarcraft.stargate.Stargate;
 import org.bukkit.Material;
 import org.junit.jupiter.api.BeforeAll;