Fix ARGS4J-25 - support args like "-coll val1 val2 -coll val3"

Fix [ARGS4J-25](https://java.net/jira/browse/ARGS4J-25) - support args like `-coll val1 val2 -coll val3` with `@Collection(name="-coll", handler = StringArrayOptionHandler.class, …)`

Fix: 
```
java.lang.IllegalArgumentException: array element type mismatch
at java.lang.reflect.Array.set(Native Method)
at org.kohsuke.args4j.spi.ArrayFieldSetter.doAddValue(ArrayFieldSetter.java:67)
at org.kohsuke.args4j.spi.ArrayFieldSetter.addValue(ArrayFieldSetter.java:56)
at org.kohsuke.args4j.spi.StringArrayOptionHandler.parseArguments(StringArrayOptionHandler.java:75)
at org.kohsuke.args4j.CmdLineParser.parseArgument(CmdLineParser.java:440)
```