adding iono processing attributes to GUNW

[mgovorcin]

Adding ionosphere processing additional attribute to GUNW packging of ionosphere correction layer.

• Added attributes to ionosphere GUNW layer metadata:
  1. ionosphere processing_steps - list: a) iono-long wavelength: ['subband', 'rawion', 'filt_gaussian', 'geocode'],
     b) iono-long wavelength+az_shift per bursts: ['subband', 'rawion', 'filt_gaussian''ionosphere_shift', 'ion2grd', 'esd', 'geocode']
  2. water_mask filename str -. e.g. swbdLat_N47_N50_Lon_W072_W067.wbd (SRTM SWBD water mask) or '' for None
  3. mask_connected_component_zero flag - str(True/False): Mask out unwrapping connected component 0 after unwrapping lower and upper band
  4. do_phase_bridging flag - str(True/False): apply simple phase bridging between unwrapped components to minimize unwrapping error, i.e., 2pi jumps
  5. estimate_burst_jumps flag - str(True/False): estimate burst jumps, aka azimuth shift per burst (scalloping effect - miscorregistration) caused by high ionosphere delay. NOTE depends on the quality of the long-wavelength ionosphere delay estimate from split-spectrum.
  6. burst_jumps_description - str - description of this processing mode, as mentioned above
  7. swath_mode flag - str(True/False): estimate ionosphere correction per swath, this mode get turn off for cross S1A/B interferogram pair, or when the starting range is different between reference and secondary image
  8. swath_ramp_removal - str(True/False): remove ramps between swaths, adjustment in swath mode. By default is turn off
  9. swath_mode_description -- description of this processing mode, as mentioned above
  10. multilook_az_rg1 - list - multillooking ration in azimuth and range direction in the first round for iono compution
  11. multilook_az_rg2 - list - multillooking ration in azimuth and range direction in the second round for iono compution
  12. iono_height - str - ionoshere height for the thin ionosphere shell in km, needed for projection from ground2iono which is turned off by default