Add in spec.response, convolution options to rrtm

[serbinsh]

We should bring in the spec response, FWHM response function tools into rrtm

library(PEcAnRTM)
data(sensor.rsr)
 refl <- PEcAnRTM::spectral.response(as.vector(rrtm::prospect5(mod.params[i,"N.mu"],mod.params[i,"Cab.mu"],
                                                                mod.params[i,"Car.mu"],
                                                                mod.params[i,"Cbrown.mu"],mod.params[i,"Cw.mu"],
                                                                mod.params[i,"Cm.mu"])$reflectance), 'licor')

Would like to remove the depends on PEcAn RTM.

this is probably not to challenging to move from RTM to rrtm

[serbinsh]

@ashiklom I just created a new branch that added rsr based on the pecan rtm implementation. Will make a PR now

> refl <- rrtm::spectral.response(as.vector(rrtm::prospect5(1.38,41,9,0.06,0.00560,0.002)$reflectance), 'licor')
> trans <- rrtm::spectral.response(as.vector(rrtm::prospect5(1.38,41,9,0.06,0.00560,0.002)$transmittance), 'licor')
> 1-trans-refl
[1] 0.9511892 0.9066594 0.1452508