Merge wrensec-build-tools dependency with this project

[pavelhoral]

I think we should reduce number of projects we maintain and wrensec-build-tools can be easily replaced with assembly artifact generated by this projects.

Various build configuration (checkstyle definitions, JavaDoc styles, Maven site configuration) can be stored inside this project and deployed as additional artifacts with classifier (e.g. wrensec-parent-3.2.0-checkstyle.jar). This will reduce our maintenance overhead and it makes sense to update parent every time build configuration changes.

[pavelhoral]

I have played with this idea a bit (pavelhoral@8cde7f1) but decided that I am not ready to commit to this yet. Not quite sure whether this is a nice solution to a real problem or an ugly hack (having parent to produce additional artifacts).