Simplify JSF assistant

This PR tries to simplify Java ServerFaces assistant a bit. The main change is that all Maven dependecies will be downloaded from Maven Central, similarly as it is in Maven assistant now. There are other changes as well, e.g.:
- added ability to run the project with "mvn jetty:run"
- all classes now live in org.devassistant.jsf namespace
- dropped spec file, since packaging project which is not self-contained doesn't make sense (IMO)
- fixed various warnings and typos