Script to apply thermal noise correction and radiometric normalization

[seongsujeong]

This PR is to add a python script to apply thermal noise correction and / or radiometric normalization applied. The noise correction can help reduce the boundary between the subswaths in Sentinel-1 frame. Radiometric normalization can be useful to reduce the discontinuity between the tracks.

TODOs:

• Discuss the necessity of more complex mosaicking algorithms (e.g. "close-to-centroid" mode)
  • Decided not to implement after discussion
• Support for EPSG4326, especially for the case of anti-meridian crossing
  • The script in this PR will be focused on applying the correction & normalizations rather than mosaicking algorithm.

Below are the examples of the correction results

1st image: Before thermal noise correction and radiometric correction
2nd image: After thermal noise correction and radiometric correction. (output from this PR)
The 1st and the 2nd image are in the same color scale.
3rd image: RTC result. Note that this plot has different color scale than the previous two.