GUACAMOLE-635: Require Java 1.8 for all Java components except guacamole-common.

extensions/guacamole-auth-radius/pom.xml

@@ -37,14 +37,14 @@
     <build>
         <plugins>
 
-            <!-- Written for 1.6 -->
+            <!-- Written for Java 1.8 -->
             <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
                 <version>3.3</version>
                 <configuration>
-                    <source>1.6</source>
-                    <target>1.6</target>
+                    <source>1.8</source>
+                    <target>1.8</target>
                     <compilerArgs>
                         <arg>-Xlint:all</arg>
                         <arg>-Werror</arg>