setting for scriplets in rpm files should be Seq[String] instead of Option[String]

[Kreinoee]

Inspired from: #219

I think that is more likely that users want too add more commands to scriptlets, than to replace them entirely. This is extra proplematic because predefined settings like packageArchetype.java_server adds some scriplets, that is pretty easy for the user to override by mistake.

Currently ekstra scriplet commands can be added like this:

rpmPre <<= (rpmPre, linuxScriptReplacements) apply { (pre, replacements) =>
      Some(pre.map(_ + "\n").getOrElse("") + "Your new content\n")
}

but it is pretty complex and not very intuitive. I think most sbt users would expect to do this:
rpmPre += "some usefull shell command"

[muuki88]

I think this is a pretty decent approach. IMHO we should extend this to the debian packaging as well.
However I like the approach where you can provide a complete control script. So we may also add
an option controlScriptStrategy (or something like that), with values like file, settings, merge and fail.

This would makes things a lot easier in the debian package, where we add chown and useradd statements with a lot of action. It would be just postInst += "....".

[muuki88]

I will start this after #348 is merged. If you use the java_server archetype you can already add stuff the rpm scriptlets via files. Just put them in src/rpm/ - postinst postun preinst preun