FgBioMain is not easily extended

[nh13]

It has both FgBioCommonArgs and FgBioTool hard-wired in the makeItSo method.

[tfenne]

FYI I looked at this and it's not easy (not possible?) to do without breaking backwards compatibility a little bit. I was hoping we could just add type members e.g:

class FgBioMain(...) {
  type Command <: FgBioTool
  type CommonArgs <: FgBioCommonArgs
}

that would allow subclasses to override them. But type members cannot have the necessary : ClassTag, that is needed to do all the reflection hijinks in that class. So I think the only solution is to change the declaration to:

class FgBioMain[Command <: FgBioTool : ClassTag, Args <: FgBioCommonArgs : ClassTag](..) {

but that will break any other places the class is instantiated, because it will now require the type params to be supplied.