Remove lambda_abs in SurfaceKinetics

[KulaginVladimir]

I think $\lambda_\mathrm{abs}$ is redundant here and makes the BC less flexible.

We can redefine $k_\mathrm{bs}$ as: $k_\mathrm{bs}\lambda_\mathrm{abs}\rightarrow k_\mathrm{bs}$, so $k_\mathrm{bs}$ could be named as the rate constant of transition with units of $[m s^{-1}]$.