quantity.Discrete/zeros will return an empty array if the requested size for zeros contains 0 as size. quantity.Discrete/compose works on quantities defined on quantity.EquidistantDomain

Change the parameter order of quantity.*/diff
Now, the domain name wrt which the derivative should be taken is the second argument and the order of the derivative is the third.

speed up of the unittest utilizing setupOnce

Thus, also the TimeDelayOperator is working for such functions.

except some points, that must be discussed for the quantity.Symbolic, the implementation of quantity.Domain seems to be nearly finished.

Fixed #16: multiplication of symbolics is working again

Added symbolic evaluation of quantity.Symbolic. (This is necessary for some strange functions, see e.g. the corresponding unittest)
Simplified the "isempty" check for quantities

Added converter of quantity.Discrete to quantity.Function: a linear interpolation is used as valueContin$

- setName() for setting names of all elements of a quantity array
- transpose() for transposing quantities: now call by value and change of name
- flipGrid() changes name now