Improve navigation bar (#890)

* Remove Raspberry pi Docker file

* Remove old show-source/solution and plan button

* Remove commented out code

* Improve navigation

* Remove underline from navigation and remove margin of left navigation button

* Make arrow a bit smaller so it aligns a bit better with the navigation bar itself

webgoat-server/src/main/docker_rpi3/Dockerfile

@@ -1,10 +0,0 @@
-# Baseimage specially for raspberry pi usage
-FROM resin/rpi-raspbian:jessie
-VOLUME /tmp
-# Installing openjdk-8-headless like in the standard Webgoat Docker container
-RUN apt-get update && apt-get install -y \
-      openjdk-8-jre-headless
-RUN cd /root; mkdir -p .webgoat
-ADD webgoat-server-8.0-SNAPSHOT.jar webgoat.jar
-RUN sh -c 'touch /webgoat.jar'
-ENTRYPOINT ["java","-Djava.security.egd=file:/dev/./urandom","-jar","/webgoat.jar"]