Changed Client.java

This update makes Client.java configurable from a parent project's pom file either through command line arguments (<arguments> below) or through an external property file (<systemProperties> below). 
             <plugin>
                <groupId>org.codehaus.mojo</groupId>
                <artifactId>exec-maven-plugin</artifactId>
                <executions>
                    <execution>
                        <goals>
                            <goal>java</goal>
                        </goals>
                    </execution>
                </executions>
                <configuration>
                    <mainClass>de.dailab.plistacontest.client.Client</mainClass>
                    <arguments>
                        <argument>teamid.properties</argument>
                        <argument>de.dailab.plistacontest.recommender.ContestMPRecommender</argument>
                    </arguments>
                    <systemProperties>
                        <systemProperty>
                            <key>plista.team</key>
                            <value>${basedir}/${plista.teamid}.properties</value>
                        </systemProperty>
                    </systemProperties>
                </configuration>
                <version>1.2</version>
            </plugin>