Labels used to get event data are now configuration options of modules

The modules used in dataGen are now configured by passing the labels
the modules will use to get/put data from/to the Event. This is more
inline with how actual experiment code is handled and makes it clearer
how the modules are connected.
Merge pull request #3 from Dr15Jones/configureInAndOut

Labels used to get/put event data are passed to module constructors
Reviewed and merged.