Fix bugs in ContinuousOperator
Created by: PhilipVinc
In the last big PR I had assumed that the potential energy function of ContinuousOperators shuold be a vector, but that was not the case.
Now Potential
should work both with functions that return a scalar and a vector.
Also makes this enables Squared[ContinuousOperator]
to work.
Also removes the rudimentary chunking that @gpescia had implemented for continuous operators in order to use the new one