Saving features to the postgres server needs a speedup or progress monitor

[KevinMcGee]

Saving feature sets to the postgres server works, but it can take a while depending on how many features are detected. For example, saving 1121 features took about 3 minutes while saving only 93 features only took a few seconds.

The problem is that OSN does nothing to report that this is the operation it is performing. It looks like it's hanging after reporting how many features are detected, when really it's saving the feature set to the server.

Either a progress monitor should be implemented in order to inform the user what is happening, or we should look into ways of speeding up the process.

From @geovations: "there may be some things we can do from the GDAL side to speed that up, like bulk insert, COPY, stuff like that"

depends on DigitalGlobe/DeepCore-Dev#371

[avitebskiy]

@LetThereBeDwight is working on the vector reading story. As a part of the work he's doing he will expose transaction support for vector feature sets. This should help with database performance.