Running uberjar for the server

This PR creates a template `-main` for running the application. The only mode supported at the moment is an integration mode. This will allow us to launch the sandbox for engineering to start tinkering with.

I also changed the name of `create-local-image-storage` to `create-image-storage` to better reflect the abstraction.

I also fixed a minor discrepancy with the `option-map` in `vignette.util.thumbnail` that enables the modes to be sent to the thumbnail script properly.

The build/run process is as follows:

```sh
lein uberjar
java -jar vignette/target/vignette-standalone.jar -I -p 8081
```

/cc @nmonterroso 
The only thing I'd consider is whether or not to throw the exception. It gets caught up the request chain, but it also logs a message to the logger, so we'd be sending two messages for one error. 

Maybe we can make a custom exception object with a context?