Add (P)edantic Maven profile to run a battery of code analysis plugins

The profile can be activated by adding "-Pedantic" to the Maven command or by any other means of
activating profiles (see https://maven.apache.org/guides/introduction/introduction-to-profiles.html).
Be aware that running all those checks takes some time and the build time increases significantly
when the pedantic profile has been activated.

The profile executes the following Maven plugins:

* FindBugs Maven Plugin (http://mojo.codehaus.org/findbugs-maven-plugin/); skip with "-Dfindbugs.skip"
* Maven PMD Plugin (https://maven.apache.org/plugins/maven-pmd-plugin/); skip with "-Dpmd.skip"
* Maven Checkstyle Plugin (https://maven.apache.org/plugins/maven-checkstyle-plugin/); skip with "-Dcheckstyle.skip"
* Cobertura Maven Plugin (http://mojo.codehaus.org/cobertura-maven-plugin/); skip with "-Dcobertura.skip"

The individual Maven sites (with HTML reports of the code analysis plugins) can be generated with `mvn -Pedantic site`.