Add image alias

[johnstob]

This PR is to introduce the initial SICD alias removal tool.

It has been added to the single entry point CLI

usage: skp sicd_alias [-h] [--threshold THRESHOLD] [--num-iters NUM_ITERS] [--zones ZONES [ZONES ...]]
                      [--symmetric] [--dilate DILATE] [--prf-override PRF_OVERRIDE]
                      input_sicd_filename output_sicd_filename

Clean up PRF alias energy from a SICD

positional arguments:
  input_sicd_filename
  output_sicd_filename

options:
  -h, --help            show this help message and exit
  --threshold THRESHOLD
                        Threshold to use when creating NIFT mask (units of stddev) (default: 9)
  --num-iters NUM_ITERS
                        Number of iterations of cleaning to do (default: 2)
  --zones ZONES [ZONES ...]
                        PRF multipliers to search for alias energy (default: [-2, -1, 1, 2])
  --symmetric           Search positive and negative of zones (default: listed zones only, not their inverse)
  --dilate DILATE       Number of pixels to dilate the masks (default: 1)
  --prf-override PRF_OVERRIDE
                        Override the PRF with a fixed value

Below are before/after PNG of TTG SICD with aliases introduced/mitigated:

Before	After