+1 to standard and available to all entities.

Whether it's an external file manager class, not entirely sure.
There was also a passing comment in some other pull request about maybe making more use of something like the `ScriptRunner` interface: perhaps there'd be a `driver.getScriptRunner()` or `driver.getResourceThing()` so related methods were kept together somehow. But I'm not sure what names those would have.

Related (but not for this pull request!), various things currently do `sshDriver.getMachine().exec(...)` which made it hard for us to customize the ssh flags used for invocations by a particular entity. Rationalising all of these exec, copy, etc methods would be great.

The method names and signatures on AbstractSoftwareProcessSshDriver, SshMachineLocation and SshTool are all over the place.