shp2pgsql: Add GeoPackage vector support (gpkg2pgsql)

[sfkeller]

The GeoPackage OGC standard format has many advantages over Shapefiles. Therefore extending shp2pgsql with this (vector) format - or complementing shp2pgsql with aka "gpkg2pgsql" loader) makes sense.

[robe]

Probably separate will be better as it would require adding in a new SQLite dependency

[pramsey]

I'd be tempted to close this with a "no". At some point we're just duplicating functionality from ogr2ogr. Much as I love geopkg, I don't see how taking on this additional maintenance overhead helps us, given the relatively low penetration of the format still.

[robe]

Only reason I would say not to close it is some folks are stuck with gdal 1.11. Doesn't that predate geopackage. Then again by the time we implement everyone will be running 2.0 gdal or above anyway so might make more sense to say "no". I'll push to the fund me category.

Anyrate not something we should jump into without having someone wanting to take on the job of supporting it. Not something I'm interested in doing as there are higher things on my priority list of support.

[sfkeller]

"Fund me" looks good to me.

Avoiding maintenance of duplicated code makes sense. I assume there are reasons to maintain a bulk loader in PostGIS, since this relieves users to install OGR/GDAL separately.

My pondering is, as long as it's shp2pgsql this does'nt help penetration of better formats. So, consequently one could deprecate and/or removing shp2pgsql completely.

In any case, a hint to OGR and better alternatives to Shapefiles (somewhere like in the shp2pgsql docs and/or the tool header?) would be IMO worth to be considered.