* Included a concept for an observable
* Modified the (parallel) metropolis simulation to check the concept of the observable in the functions.

Fixes #32
Renamed the template parameter of the metropolis like simulatrions from "Observable" to "Observator", because the object given must have a function returning an observable, but it is no observable.
* Introduced the new concept check class "ObservatorConcept" for checking the type of observable functor.
* Used the new concept check in class in the metropolis and metropolis_parallel functions

Fixes #33
Removed the two files. Will be extended later on.
Merge branch 'master' of https://github.com/bkrueger/mocasinns