Remove environment-variables from command

It turns out that you cannot do it this way.  By the time the
environment variables are changed they've already been checked.  If we
want to set these for real we might have to shell out and run another
command with these environment variables set.
Change HASH to Text (json encoded)

Since you cannot shortcut on a HASH type input, we json encode all such
inputs (in the input_hash method) and then decode it in the Result
object.
Update plan_files for file-based changes