Add function move FCDA data. 

As a user of this library, I want to be able to change the order of FCDA element in a DataSet. I want the library to make sure that the confRev of all connected control blocks is updated.

`function moveFCDA(fcda:Element, relativePisition: number): Edit[]`

**Requirements**
- return empty array when `relativePosition` points to an invalid spot. 