Contribution guide

Please carefully read this document before contributing to the project and submitting a pull request.

Source code

The Google source code style guidelines (https://google.github.io/styleguide/cppguide.html) are adopted, the only exception being names of private class data members. In our convention, those names are prefixed by an f, as in GEANT4.
```
int fSomePrivateMember;
```
Class names are generally prefixed with RMG. Purely virtual class names with RMGV.

RMGMasterGenerator is the remage mandatory concretization of G4's G4VUserPrimaryGenerator. An instance of this class is passed to G4 as user action. This master class manages remage generators