reconstruct at location

[lucywowen]

We should also add an option to allow the user to specify locations as 3D coordinates. that would allow them to specify location that weren't already in the model, which would make the syntax more general. e.g. a future version could work as follows:

if recon_loc_inds is None, reconstruct at all model locations
if recon_loc_inds is an array, reconstruct at those inds in the Model object
if recon_loc_inds is a matrix with 3 columns, reconstruct at those MNI locations (even if they're not in the model; may require blurring out the model to those locations)