Feature/3985 pm manifest support for copied files

[euler-room]

Add a subclass, Manifest::Template", which allows for the inclusion of:
files: ['.../file1', '.../directory1/file2', '.../directory2', '...etc']
key/value pair in the template manifest file.
This is serialized as:

---
files
- '.../file1'
- '.../directory1/file2'
- '.../directory2'
- '...etc'

when to_yaml is called on an instance of Template::Manifest