travis: improve build process and expand build matrix

Make a build heriarchy to reduce images size.
Add Android Things builds to build matrix.
Drop gcc-4 builds, use gcc-5 and gcc-6 instead.
Add SonarQube static analysis scans.

Signed-off-by: Nicolas Oliver <dario.n.oliver@intel.com>

docker/Dockerfile.java

@@ -0,0 +1,15 @@
+FROM upm-base
+
+# Update apt-get
+RUN apt-get -y update && \
+    # Java Build Dependencies
+    apt-get -y --no-install-recommends install libmraa-java \
+    default-jre default-jdk
+
+# Configure Java Home
+ENV JAVA_HOME /usr/lib/jvm/java-8-openjdk-amd64/
+
+# Set Workdir
+WORKDIR $UPM_SRC_DIR
+
+CMD bash