Mod reco

Changed reconstruction stage to a similar scheme as the new oscillation stage (base service with several derived services). This should allow for easier adding of alternative reco methods. E.g. parametrized reco, which is to follow soon.
I decided that it is an *option to the developers* here and not to the users, so that's why I left it in the costructor but did not leave it as something to change in the `settings.json` file. I don't see any problem with this approach.