Bump up gestalt version to 5.1.5

Author: DarkWeird

engine/build.gradle

@@ -133,8 +133,8 @@ dependencies {
     compile 'com.jagrosh:DiscordIPC:0.4'
 
     // Our developed libs
-    compile group: 'org.terasology', name: 'gestalt-module', version: '5.1.4'
-    compile group: 'org.terasology', name: 'gestalt-asset-core', version: '5.1.4'
+    compile group: 'org.terasology', name: 'gestalt-module', version: '5.1.5'
+    compile group: 'org.terasology', name: 'gestalt-asset-core', version: '5.1.5'
     compile group: 'org.terasology', name: 'TeraMath', version: '1.4.0'
     compile group: 'org.terasology.bullet', name: 'tera-bullet', version: '1.3.1'
     compile group: 'org.terasology', name: 'splash-screen', version: '1.0.2'