Changed default jre/java flags

Changed the default given java-flags to a more server-side configuration
-XX:+UseConcMarkSweepGC 
-XX:+UseParNewGC 
-XX:+CMSIncrementalPacing 
-XX:ParallelGCThreads=2
-XX:+AggressiveOpts

Author: KoEnix

Dockerfile

@@ -54,7 +54,7 @@ WORKDIR /data
 ENTRYPOINT [ "/start" ]
 
 ENV UID=1000 GID=1000 \
-  JVM_XX_OPTS="-XX:+UseG1GC" MEMORY="1G" \
+  JVM_XX_OPTS="-XX:+UseConcMarkSweepGC -XX:+UseParNewGC -XX:+CMSIncrementalPacing -XX:ParallelGCThreads=2 -XX:+AggressiveOpts" MEMORY="2G" \
   TYPE=VANILLA VERSION=LATEST FORGEVERSION=RECOMMENDED SPONGEBRANCH=STABLE SPONGEVERSION= FABRICVERSION=LATEST LEVEL=world \
   PVP=true DIFFICULTY=easy ENABLE_RCON=true RCON_PORT=25575 RCON_PASSWORD=minecraft \
   RESOURCE_PACK= RESOURCE_PACK_SHA1= \