[FEATURE] ScriptAPI: Allow devs to set flag for more aggressive optimization

[SenkJu]

Nashorn has a flag that optimizes scripts much more aggressively. This can significantly improve performance, but some scripts may not work properly. Also, the time needed to compile the script increases dramatically.
For this reason, script developers should be able to set the flag manually, as long as it works with the script.

Note:

NashornScriptEngineFactory().getScriptEngine("--optimistic-types=true")

[SenkJu]

Custom flags can be passed like this:

/// engine_flags=-ot=true,--language=es6

List of all available flags can be found using

> jjs -xhelp