Issue #14 expose %config and %noreplace directives

Simple solution built to resemble sample from Redlilne

```xml
<rpmfileset prefix="/tmp/rpmtest/conf" config="true" noreplace="true" file="conf/test1.conf"
              filemode="644" username="none" group="none"/>
```
(i.e. config="true" noreplace="true")

and current handling of file owner / file mode like this:

```xml
            <mapping>
                <directory>/etc/some/config</directory>
                <!-- ... -->
                <config>true</config>
                <noreplace>true</noreplace>
                <sources>
                    <source>${project.basedir}/target/someFile.txt</source>
                </sources>
            </mapping>
```

Someone may add a full Directive handling (as Redline seems to support it well in the Java API) but this would require some more complex design decisions about how the XML for that should look like, so this is at least a shortcut.