implemented all neutron source rate functions. Now the fun part of debugging starts...
Added a Nummerical Integrator. That can take variable function as input.
added a prototype of the Nintergator to the function list.

changed the Class I ions surfival function so it used the new Nintergrator function
alted the Ic2 function to use the new NIntegrate function.

This revealed a bug where the Interpolation dus not work when r is the same size as R_max in the RTable. This is now fixed.
update the Ic4 function with the new NIntergrate function