build and ship javadocs for the Project

[Schmoho]

javadoc is more or less the default way of generating human-readable code documentation from java projects. We are already adhering to the documentation style that javadocs expects to work properly, so we should (barring any licensing issues, which I doubt)

• include the docs in version control
• include building the documentation in the build jobs
• consider if it is feasible to host them somewhere

[Schmoho]

I have added a gradle build task and included the built javadocs on the 2.1 branch.

I have also set up GitHub pages for this repository to link to the javadocs on the 2.1 branch: https://draeger-lab.github.io/ModelPolisher/

@draeger is this okay? can we use another webserver to serve some static HTML?

[draeger]

Thanks for doing that, @Schmoho!