Ogr view model

Added an ogrItemViewModel that forwards files to our ogr2ogr service for conversion.
On drag and drop the file is uploaded to the server on a url it is loaded by the server.
Made this the default fall through for formats we don't have explicit handlers for.
Put 1MB size constraints on server and client side
Added airports.zip (shape file) to our init_test.json list

Is this the best name for this?  It seems to me that OGR is largely an implementation detail.  The important bit is that this view-model calls out to a conversion service.  Maybe something like `ConvertedItemViewModel`?