update maven pom

embed properties that were in a local settings.xml
fix tag names and properties that have changed from maven 2 and new plugin versions
specify compiler plugin version.

pom.xml

@@ -7,6 +7,12 @@
     <version>0.0</version>
     <name>app</name>
     <url>https://eng-git.canterbury.ac.nz/SENG302-2016/team-0</url>
+
+    <properties>
+        <maven.compiler.source>1.8</maven.compiler.source>
+        <maven.compiler.target>1.8</maven.compiler.target>
+    </properties>
+
     <dependencies>
         <dependency>
             <groupId>junit</groupId>
@@ -15,8 +21,14 @@
             <scope>test</scope>
         </dependency>
     </dependencies>
+
     <build>
         <plugins>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-compiler-plugin</artifactId>
+                <version>3.5.1</version>
+            </plugin>
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-shade-plugin</artifactId>
@@ -26,8 +38,8 @@
                         <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
                             <manifestEntries>
                                 <Main-Class>seng302.App</Main-Class>
-                <X-Compile-Source-JDK>${maven.compile.source}</X-Compile-Source-JDK>
-                <X-Compile-Target-JDK>${maven.compile.target}</X-Compile-Target-JDK>
+                                <X-Compile-Source-JDK>${maven.compiler.source}</X-Compile-Source-JDK>
+                                <X-Compile-Target-JDK>${maven.compiler.target}</X-Compile-Target-JDK>
                             </manifestEntries>
                         </transformer>
                     </transformers>
@@ -55,9 +67,8 @@
                 <artifactId>maven-pmd-plugin</artifactId>
                 <version>3.6</version>
                 <configuration>
-          <linkXref>true</linkXref>
-          <targetjdk>1.8</targetjdk>
-          <minimumtokencount>100</minimumtokencount>
+                    <linkXRef>true</linkXRef>
+                    <targetJdk>${maven.compiler.target}</targetJdk>
                     <rulesets>
                         <ruleset>/rulesets/java/basic.xml</ruleset>
                         <ruleset>/rulesets/java/imports.xml</ruleset>