Finish adding non-interactive mode swtich

[markgw]

By default, we run in interative mode, assuming the user's at a terminal

This switch tells interface components that they can't expect input from a user

This should mean, for example, that we don't display progress bars, whose output looks bad when piped to a file

The parameter can be set using the environment variable PIM_NON_INT to 1 (implemented) or the cmd line switch --non-interactive (not implemented).

• TODO Add this to the documentation
• TODO Use this to hide progress bars, etc
• TODO Allow this to be set on the cmd line

NON_INTERACTIVE_MODE = len(os.environ.get("PIM_NON_INT", "")) > 0

[markgw]

Mostly done now.

Still need to add to documentation.