remus::JobResult should be more like JobSubmission

Currently JobResult can only contain a single file / data blob. It needs to be updated to handle any number of these, just like JobSubmission. 

I don't know if it should have the same arbitrary key/value as JobSubmission or should have something like:

```
JobResult jr;
jr.setMesh( remus::common::FileHandle() )
jr.setMode( remus::common::FileHandle() )
```
