REPL and Pooled Resources

This primarily an attempt to solve the 20K issue noted in issue #265. The first patch preps the razor executable to become a long running service. This was achieved by extending the basic CLI interface with a batch/repl mode. The second patch utilizes a resource pool to limit the number of razor executables spawned in the api. The third patch does the same for IO in the image service.

The combined result is a snappy API that can handle relatively large loads. Some stacking will still occur, but is now much less severe. On my test system the load profile has been flipped: the perftest itself consumes more resources than the razor api and image service.

I'm interested to know what kind of performance you experience with this patchset!