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.
`RecoServiceKDE` was developed independently by Tim and is not part of the pull request (as of now). I haven't gotten a pull request from Tim yet, but when it comes I will make sure that it also contains documentation.