Allow passing custom java args

[qu1ck]

Startup script has hardcoded java -jar <path to jar>.
There should be a way to pass custom arguments to it, things like -Xms, -Xmx, flags for GC tuning etc.

[renjfk]

things like -Xms, -Xmx

Normally you shouldn't need to set these flags with the UseContainerSupport flag, which is enabled by default if supported by the system.

However, there's already the JAVA_TOOL_OPTIONS environment variable that you can use for this purpose.