[Connection][Storageelement][Drone]Restructure interplay to enable flexible configurations of multiple sites

[HerrHorizontal]

The current treatment of one connection module to one RemoteStorage needs to be expanded to an arbitrary number of connection modules interfaced to arbitrary numbers of storage elements.

Moreover the focus on remote storage elements needs to be dismantled, since there should be no different treatment between a connection to any storage, except for parameter values.

Rather there should be distinct StorageElements which have a distinct connection and are matched to a specific site. (Also have a look into issue #7.)

[HerrHorizontal]

@tfesenbecker proposed to create a site module, which will include the functionalities of matching drones, storageelements and connections to a particular site.

This could also be recursively invocable to combine sites into a single one, while keeping the precise treatment of each.

[HerrHorizontal]

This also involves changes as mentioned in issue #9 .