add tomcat7 plugin additional configuration

provide additional configuration to tomcat7-maven-plugin so we're able to

• provide an executable war (cfr. http://tomcat.apache.org/maven-plugin-2.1/executable-war-jar.html)

• enable tomcat7:run, so we're able to debug and change code without recompiling the whole source (cfr. http://tomcat.apache.org/maven-plugin-2.1/run-mojo-features.html)