regression application csv output

[pritesh-mehta]

#372 forces the use of the identity aggregator in the case of output that is not the same shape as the input image e.g. single value regression. The identity aggregator saves output as nifti images. This behaviour is enabled by a config flag -force_output_identity_resizing. A more desirable solution would be to not have a flag in the config and in the case of non-image output, pass through the resize sampler to produce a CSV output only (nifti images containing a single value are unnecessary).

[pritesh-mehta]

The need for a flag may be negated by specifying a csv output if the csv reader is used for label input.