This PR includes

• Support to create a debian package with the java bindings (libsgpp-java)
  • adds javahelper as a dependency on the developer machine that is to create the debian packages. Javahelper ist used in order to correctly insert the jar file into /usr/share/java
• Travis tests for the new libsgpp-java package. The package is built, installed and all three SGpp Java examples are run with it.
• A fix for the refinement java example and various other small improvments (package descriptions, gitignores for temporary files)

Note:

• Given the sparse occurrence of java examples in our code I would consider this Java Debian package as experimental as I could only test it with our small examples so far. I think it should still be included as it is the only way to use the Java bindings together with the normal libsgpp Debian package (without the user having to build SGpp himself anyway).
• To use this package. the Java classpath still needs to be set to /usr/share/java in order to find the bindings.