Create new Samples project with strong focus on best practices

- [ ] App samples (@jonsequitur) 
  - [ ] Using parser without actions
  - [ ] Using the parser with actions (simple case)
  - [ ] Intercepting and replacing actions
- [ ] How to test command line parsing (@jonsequitur) 
- [ ] How to create testable applications with S.CL without the need of using DI (@jonsequitur)
- [ ] Extensibility points (@adamsitnik)