[rules-dev] Do not use -Dmaven.test.skip (=decrecated), use -DskipTests (instead)

Since IIRC maven 2.0.8, -Dmaven.test.skip has been replaced by -DskipTests. Use skipTests (see README.txt). *If you're were still using the maven.test.skip, you 'll now find out that the build fails on drools-compiler* because drools-compiler has a test-jar dependency on drools-core (as well as a normal dependency on drools-core). The skipTests compiles and builds the test-jars (just doesn't run the tests), while maven.test.skip doesn't even compile or build the test-jars (which is not much faster). -- With kind regards, Geoffrey De Smet