Shapefile import is slow

[mattwigway]

I always thought that this was due to the shapefiles themselves, but even when importing GeoBufs, which should be blazing fast, the shape feature stores are dog-slow.

[mattwigway]

It's to the point now where importing a 119k feature shapefile times out the proxy server.

[mattwigway]

Two things appear to be causing much of the slowness:

1) Converting attribute names to attribute IDs - we can just cache the attribute IDs. 2) reverse-sorting the features by ID. Since the IDs are arbitrary, we can just assign them in such a way that the are presorted, then we won't have to sort them.