Repeated JVM command line options are not preserved

[pditommaso]

Java 9 allows the use of the --add-opens command line option multiple times specifying different package names.

However when invoking Capsule with more than one --add-opens option only the last one is preserved in the resulting command line returned by Capsule, breaking the target application.

The error suggests that JVM options are collected by using a Map, a List should be used instead.