Overlapping file extensions

[rimutaka]

Pascal and Puppet share the same .pp file extension. Pascal files are processed as Puppet files at the moment.

1. The syntax for expressing muncher selection params other than the path is there, but it is not implemented.
2. Find the most efficient way of matching a muncher on file content or sibling files (e.g. presence of a project file)
3. Implement the next level of muncher selection for [2]

Thanks to @JohnPeel for picking it up.

Relates to #39