ENH: add "repair" and/or "salvage" option to on_invalid parameter in read_dataframe

[theroggy]

The on_invalid functionality in read_dataframe always results in None geometries now.

It would be interesting to also have a "repair" and/or "salvage" option, so it becomes possible to recover data if possible.

In theory this should be possible:

• EDITED: in GEOS, there is apparently a function GEOSWKBReader_setFixStructure_r that enables fixing such issues when parsing WKB's. Support to use this could be added to shapely.
• Or via another library, but this most likely implies extra dependencies which might not be ideal for an edge case like this.
• Or an option to get back the WKB's instead of trying to read them, so you can salvage yourself
• ...

xref #422

[theroggy]

I encountered a function in GEOS, GEOSWKBReader_setFixStructure_r that seems to enable fixing such issues when parsing WKB's. Support to use this could be added to shapely.

This seems like a reasonable path forward for this case.

[EwoutH]

Thanks for looking into this! Exposing an existing function sounds like an very elegant way to implement this.