Use Sentinel-1 GRD image products as input

[mcgarth]

Consider whether Sentinel-1 GRD products can be directly used for this target analysis (validate against data generated from SLC via Gamma).

If they can, the advantage is that users do not need to first use some other processing software (Gamma, SNAP, etc) to generate input images for CoRAL.

[mcgarth]

Since CoRAL relies on co-registered image stack as input, additional functionality would need to be coded (or borrowed from other packages) as follows:

• a cross-correlation algorithm to align GRD images
• an algorithm that converts lat/lon CR positions in to radar range and azimuth coordinates