make serialization pluggable

allows to optionally use fast serialization as default (speeds up 8-10 times for pojos). NO dependency added.

* added ObjectStreamFactory providing ObjectOutput/ObjectInput instances
* BytesMarshallerFactory implements ObjectStreamFactory
* added an implementation of ObjectStreamFactory for JDK serialization
* lame: added global static var to VanillaBytesMarshallerFactory. I could not find a way to inject this otherwise
* added flush() statement after writing an Object.

speedup in iteration for this class is from 50k per second to 480k per second (on a slow AMD opteron 2.x Ghz)

```java
class TestRec extends Record {

    String name = "Bla";
    String other = "Bla1";
    String another = "Bla3";

    int x = 13;
    int arr[] = {1,2,3,4,5};
..
}
```
with this factory impl (requires **fst 2.0 beta !!! from releases section**):
```java
public class HugeCollectionsBinaryStorage implements BinaryStorage<String,Record> {

    public static FSTConfiguration conf = FSTConfiguration.getDefaultConfiguration();

    static {
        VanillaBytesMarshallerFactory.defaultOSFactory = new ObjectStreamFactory() {
            @Override
            public ObjectOutput getObjectOutput(OutputStream out) throws IOException {
                return conf.getObjectOutput(out);
            }

            @Override
            public ObjectInput getObjectInput(InputStream in) throws IOException {
                return conf.getObjectInput(in);
            }
        };
    }
....
}
```