Membrane profiles with diffuse Green's functions

[robertodr]

The upcoming PR #109 does the numerical integration in logarithmic scale. This requires a step size dependent on the width of the profile and the distance of it from the origin (center of the sphere). This requires some thinking to do it correctly, since a membrane has two width parameters.

The following lines of code should be reintroduced in SphericalDiffuse.hpp to re-enable the use of membrane profiles from the constructor:

  template <typename U = ProfilePolicy,
            typename = typename pcm::enable_if<
!pcm::is_same<U, dielectric_profile::MembraneTanh>::value>::type>

and the complementary SFINAE check:

  template <typename U = ProfilePolicy,
            typename = typename pcm::enable_if<
pcm::is_same<U, dielectric_profile::MembraneTanh>::value>::type>