Add inbuilt command logging capability

[parrotcar00]

Describe the problem

Whenever I write any bash script, I do this:

#!/bin/bash

set -ex

#Run some command foo
foo --bar --baz

The -x flag logs all bash commands as they're run. It's very useful when debugging things. I was looking for something that does the same in turtle.

Describe your solution
When using turtle in kotlin, I've made this helper function which I use:

fun loggedShellRun(command: String, args: List<String> = emptyList(), workingDir: File? = null): String {
    val commandString = "$command ${args.joinToString(" ")}"
    println("Exec: $commandString")
    val result = shellRun(command, args, workingDir)
    return result
}

and then I call it like:

loggedShellRun("foo", listOf("--bar", "--baz"), workingDir)

I think it would be a good idea to include this as a built in feature into the library.

Checklist

• I've read the guide for contributing.
• I've checked there are no other open pull requests for the feature.
• I've checked there are no other open issues for the same feature.

Additional context