Add initial Maven module for Dropwizard documentation

The documentation submodule is using http://tomdz.github.io/sphinx-maven/
to generate the Dropwizard documentation with Sphinx.
Fix version of maven-project-info-reports-plugin to avoid warnings
Add Maven GitHub Site plugin and bind to site phase
Add Javadoc to generated Maven sites
Use correct URL for GitHub issues
Add ciManagement to POM
Add information about mailing lists to POM
Update scm.url to use HTTPS by default
Publish GitHub Pages during `site-deploy` goal

This was rather painful. First one has to generate the aggregated site for
all sub modules by running `mvn site:site site:stage` with the parent project's
POM (ie. not inside a subdirectory) after which one can deploy the result
(which resides in "target/staging") to GitHub Pages by executing the `site-deploy`
goal for the parent project.

The distributionManagement.site stuff is required for the maven-site-plugin to be
happy and allow the execution of `site:stage` but it should not deploy to the
URL give in distributionManagement.site.url using Wagon which is why skipDeploy
has to be set to true.

To put it short: ┻━┻ ︵ヽ(`Д´)ﾉ︵ ┻━┻
Skip maven-site-plugin for dropwizard-example
Merge pull request #501 from joschi/sphinx-docs

Mavenize Sphinx docs