change compiler version to 8 and add exec plugin to maven

pom.xml

@@ -16,10 +16,26 @@
                 <artifactId>maven-compiler-plugin</artifactId>
                 <version>3.6.2</version>
                 <configuration>
-                    <source>1.7</source>
-                    <target>1.7</target>
+                    <source>8</source>
+                    <target>8</target>
                 </configuration>
             </plugin>
+            <plugin>
+                <groupId>org.codehaus.mojo</groupId>
+                <artifactId>exec-maven-plugin</artifactId>
+                <version>1.2.1</version>
+                <executions>
+                    <execution>
+                        <goals>
+                            <goal>java</goal>
+                        </goals>
+                    </execution>
+                </executions>
+                <configuration>
+                    <mainClass>de.uni_hamburg.corpora.CorpusMagician</mainClass>
+                </configuration>
+            </plugin>
+
             <!--
             https://stackoverflow.com/questions/574594/how-can-i-create-an-executable-jar-with-dependencies-using-maven
             -->