Improved scripting

[nilsjor]

Hello again ;) Reconnecting to the discussion we had here. I am proposing minor changes to improve the quality of scripting with planutils.

This PR will do the following.

• Remove the -i flag from bin/planutils. This will mean that planutilscommands will not be run in interactive mode. This means these commands will not be written to the command history. Additionally, this will fix the warnings

  bash: cannot set terminal process group (-1): Inappropriate ioctl for device
  bash: no job control in this shell

  which arise when calling planutils commands from script contexts without stdin (like docker build for instance).

• In order to preserve the interactive planutils activate environment, this is moved into its own script—which has the -i flag.
• Additionally, the planutils setup is provided with a --force flag, which allows it to be called in non-interactive shells even if it has been called before.
• Finally, the README provides a more correct on how to interactively use planutils, and is lightly touched up with syntax highlighting

[haz]

Additionally, this will fix the warnings

bash: cannot set terminal process group (-1): Inappropriate ioctl for device
bash: no job control in this shell

That little thing has been a thorn in my side for ages! Nice to see it finally fall...