wip: add copy context for file name replacement without j2 extension

[dpastoor]

This PR will allow files to be renamed by path without the j2 extension.

Eg {{proj_name}}.Rproj --> should be renamed without needing to be {{proj_name}}.Rproj.j2

This will allow IDE's to still recognize those files fine while developing the template.

As such, the current behavior will become:

• all template (.j2) files are run through the template by both name and content
• all files that aren't templates are run through by name only

non-goals

suppress whether a file should be NOT passed through the template - I'm sure that scenario may come up one day in the future, but when tangible use cases to determine how to supress/ignore/etc we can adapt the api then.