Async IO in FileSystemDataVault

[fm3]

I’m sure scala/java has support for asynchronously reading (byte ranges of) local files. That should be used in the FileSystemDataVault. This should free more threads

[fm3]

https://gist.github.com/tovbinm/f73849aff169d1ebeb97 looks similar to what we may want to do. Sounds like it may also be possible to support the byte ranges