Design and implement the file system reference mechanism for file properties

[Michael Janelle-Montcalm]

Actions can now have file properties, which point to existing files on disk. This is fine on a local computer, however the tutorials will be shared and the file paths need to point to the same data. The current system does not differentiate between absolute and relative paths, and it does not guarantee that the file will be retrievable on another distrib / computer.

The goal of this task is to design and implement a system that will ensure that the files are properly referenced. This will probably tie in with the tutorial bundling ideas, as we will mainly use this file property to access a resource. (See LP 352437 and related)