bug found where variable was used before initialesed.

changed the neutron source function so the now integrate over the right area.
added a second file which contrains all math functions. A new NIntergration function is added. This one asks for a extra input variable.

The Sfi1 makes use of the new function
altered now all neutron source function to use the NIntergrate_2 function.

Although only the first function does actually produce real numbers.
Some heavy bug fixing done. The Sfi function are working now.

The last step, calculating the Nps.
added a file for the mathmatical functions. More splitting up has to be done to keep the project neat.

A function that calculates the NPR is added. However it gets stuck somewhere.
updated the Class II ions survival function with the new integration function.