Fixing @Fork parameters overriding

[Sergey Kuksenko]

Hi,

I've found that String  @Fork parameters as jvmArgs, jvmArgsAppend and 
jvmArgsPrepend incorrectly override itself when @Fork is set both on 
class and method levels.

1. Working example:
@Fork(jvmArgs="default bla bla")
public class Foo {

    @GenerateMicroBenchmark
    @Fork(jvmArgs="yet another bla bla")
    public void bar() {
    }
}

2. Not-working example:
@Fork(jvmArgs="default bla bla")
public class Foo {

    @GenerateMicroBenchmark
    @Fork
    public void bar() {
      // should get "default bla bla" as JVM args, but don't
    }
}

The issue is fixed. New integration tests are created. Patch is attached.

-- 
Best regards,
Sergey Kuksenko