Upgrade JDK and Maven on Travis

 * JDK 1.8.0_121
 * Maven 3.3.9

.travis.yml

     - server/sonar-web/node
     - server/sonar-web/node_modules
     - $HOME/jvm
+    - $HOME/maven
     - $HOME/phantomjs
 
 before_cache:

travis.sh

 }
 
 #
-# A (too) old version of JDK8 is installed by default on Travis
+# A (too) old version of JDK8 is installed by default on Travis.
+# This method is preferred over Travis apt oracle-java8-installer because
+# JDK is kept in cache. It does not need to be downloaded from Oracle
+# at each build.
 #
 function installJdk8 {
-  echo "Setup JDK 1.8u92"
+  echo "Setup JDK 1.8u121"
   mkdir -p ~/jvm
   pushd ~/jvm > /dev/null
-  if [ ! -d "jdk1.8.0_92" ]; then
+  if [ ! -d "jdk1.8.0_121" ]; then
     echo "Download JDK8"
-    wget -c --no-check-certificate --no-cookies --header "Cookie: oraclelicense=accept-securebackup-cookie" http://download.oracle.com/otn-pub/java/jdk/8u92-b14/jdk-8u92-linux-x64.tar.gz
-    tar xzf jdk-8u92-linux-x64.tar.gz
-    rm jdk-8u92-linux-x64.tar.gz
+    wget --no-check-certificate -c --header "Cookie: oraclelicense=accept-securebackup-cookie" http://download.oracle.com/otn-pub/java/jdk/8u121-b13/e9e7ea248e2c4826b92b3f075a80e441/jdk-8u121-linux-x64.tar.gz
+    tar xzf jdk-8u121-linux-x64.tar.gz
+    rm jdk-8u121-linux-x64.tar.gz
   fi
   popd > /dev/null
-  export JAVA_HOME=~/jvm/jdk1.8.0_92
+  export JAVA_HOME=~/jvm/jdk1.8.0_121
   export PATH=$JAVA_HOME/bin:$PATH
 }
 
+#
+# Maven 3.2.5 is installed by default on Travis. Maven 3.3.9 is preferred.
+#
+function installMaven {
+  echo "Setup Maven"
+  mkdir -p ~/maven
+  pushd ~/maven > /dev/null
+  if [ ! -d "apache-maven-3.3.9" ]; then
+    echo "Download Maven 3.3.9"
+    curl -sSL http://apache.mirrors.ovh.net/ftp.apache.org/dist/maven/maven-3/3.3.9/binaries/apache-maven-3.3.9-bin.tar.gz | tar zx -C ~/maven
+    tar xzf apache-maven-3.3.9-bin.tar.gz
+    rm apache-maven-3.3.9-bin.tar.gz
+  fi
+  popd > /dev/null
+  export M2_HOME=~/maven/apache-maven-3.3.9
+  export PATH=$M2_HOME/bin:$PATH
+}
 #
 # Replaces the SNAPSHOT version by a version identifying the build.
 #
   ./clock.sh &
 
   installJdk8
+  installMaven
   fixBuildVersion
 
   # Minimal Maven settings