.files or .source options should be optional if .configure is set

[cowwoc]

Currently, if one passes in the path to a configuration file via the configure option we still get this error message:

Must set either .files or .source options

If the configuration file already specifies one of these, it shouldn't be mandatory to repeat them.

[cowwoc]

Is the code even making use of configure anywhere? I can see the code accepting it as a parameter but it doesn't look like it ever gets used. This is increasingly looking like a bug to me.