Improvements to DEA CoastLines utilities

[robbibt]

Via @GeoRach:

• Export summary table for each polygon in the shp input (incl. mean, mode 1 (and 2, 3 if several?), SD, min, max)
• Address this warning "More than 20 figures have been opened. Figures created through the pyplot interface (matplotlib.pyplot.figure) are retained until explicitly closed and may consume too much memory. "
• Add second y-axis to indicate % of dataset as line plot of histogram (optional?)
• For rate-of-change histogram plots also add n for each histogram bar (again, optional)
• Have the "interactive profile selection" tool default zoom to the preceding "statistics points histogram analysis" extent, because that's a likely user workflow
• To help novice users include both options in descriptive comments for "distance" vs "width", and None vs "*.shp" options
• For interactive polygon and transect lines, export an .shp (line or poly) so the analysis location is recorded.
• Support multiple polygons in a dataset by allowing the user to specify a field in the dataset, and loop through polygons and write to file
• Rates of change are currently different in log vs linear histogram plots due to the non-log version dropping non-significant points rather than setting them to 0 m / year change. This should be updated so values are the same for both

[robbibt]

Have incorperated these suggestions into the current version of the notebook; we can create a new issue for future improvements