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- add new functions for slope analysis: `fwa_slope`, `fwa_streamslope`, `fwa_slopewindow`
- add new function `fwa_elevation`
- include load of table `fwa_islands_poly` to database
- explicitly define geometry types in derived tables so ArcGIS does not complain
- add missing geometry indexes (14)
- add functions for creating watershed upstream of points
- expand on examples