Add convenience commands

[Harendra Kumar]

For example:

• to run a shell command purely as an effect, without using the output
• to run the command printing the full command on stdout (runVerbose)

And any other such useful utilities for day to day scripting. Utility commands that are not standard can go in a Contrib or some such module.

[Harendra Kumar]

run :: String -> IO ()
run cmd = Sh.srcWith Process.toChunks cmd & Stdio.putChunks

runVerbose :: String -> IO ()
runVerbose cmd = putStrLn cmd >> run cmd

[Harendra Kumar]

We have added toStdout and several other commands.