- cumInt does not support char inputs anymore

closes #49

quantity.Domain/find returns now "empty" values if the domain is not found. AND Cast of a quantity.Domain into a quantity.Function object.

- unittests for quantity.Domain/Discrete and /Symbolic
- deleted unittests.quantity.testSymbolic/testSolveOde

- new method remove()
- rename: renamed "copyAndRename"-method into "rename" and rewrote it

it is now adopted to the implementation of the quantity.Discrete/int/cumInt

Add a specification for boundary values in quantity.Domain

quantity.Domain: new methods real and imag

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

changed misc.diag_nd to use a for loop on the domain, which will be collapsed.

Added misc.rat to compute rational approximations of real numbers

Added quantity.EquidistantDomain to simplify the initialization of a domain with a certain step size

Fixed signals/SmoothStep to use spline wise interpolation instead of symbolic computation

Further minor fixes ...