Simplifying the template

[jtulach]

Removing default parameters (groupId, archetypeId, version, package), giving the appName more reasonable default and using packaged=true which moves the classes into appropriate package automatically.

I think this is a simpler way to write an archetype. And I think it still works. At least this is what I did to verify it:

$ mvn archetype:generate \
  -DarchetypeGroupId=org.robovm \
  -DarchetypeArtifactId=robovm-default-template \
  -DarchetypeVersion=1.0.1-SNAPSHOT
# when being asked for artefactId I have chosen xyz
$ cd xyz
$ mvn clean install
$ mvn robovm:ipad-sim

RoboVM's sample application appeared in my simulator..