More Helpful JSON / YAML Error Messages + Minor cleanup of JSON / YAML related variables in Pattern Rules

[sghoweri]

Now passing in the actual filename + path to the JSON and YAML file functions so errors are more helpful + easier to debug.

This small change makes a huge difference in projects like the Bolt Design System I run (where we're installing, versioning and publishing individual components) given that Pattern Lab by default tries to pick up deeply nested files in our component-specific node_modules folders which, unless / until patched, can often cause fatal errors w/ Pattern Lab that are close to near impossible to track down otherwise.

CC @aleksip