Working with intance methods of ResourcesFactory instead of classes.

[jadelkhoury]

Description

Instead of classes methods, we migrate to instance methods taking us one step closer to dependency injection

Checklist

• [x] This PR adds an entry to the CHANGELOG. _See https://keepachangelog.com/en/1.0.0/ for instructions. Minor edits are exempt.
• [ ] This PR expects some manual changes to the generated code. The needed changes are detailed in the CHANGELOG entry.
• [x] This PR was tested with at least one code generation, resulting in a working OSLC server.
• [x] This PR does NOT break the user block code

[jadelkhoury]

@berezovskyi

If this is a good first step, I can update the changes in the sample to reflect the latest changes (including this way). I think it might make your work with the DI easier.

https://github.com/OSLC/lyo-adaptor-sample-modelling/pull/70