Namespaces and PSR-4 compliance

One of the points I am missing in the exercises of this track is the concept of namespaces (PSR-4 compatibility). Therefore, I would like to discuss and propose the following change.

### Suggestion

Each exercise separates actual business logic from tests by having separate `src` and `test` directories. The `README.md` stays in the exercise's root folder. The example solution (and coming stub file) are going into `src` and the test file into `test`.

> The terminating class name corresponds to a file name ending in .php. The file name MUST match the case of the terminating class name.

Since there is no definition for declaration of functions pertaining to the filename, two possible solutions are crossing my mind. Either name the file `functions.php` or `exercise-name.php` - both residing within the exercise's namespace. Here I am interested in suggestions, since I haven't used a file collecting various functions in years.

### Example

Taking Bob as an example, this would result in the following structure:

- `/src` → namespace `Exercism\Bob`
- `Bob.php` (stub file)
- `example.php` (example solution)
- `/test` → namespace `ExercismTest\Bob`
- `BobTest.php`
- `README.md`

### Looking for feedback

My intention is to provide an even greater learning experience for the student within a modern (meaning current) environment.

It would be great to get some feedback on the suggestion over all and possible side effects I might not have fully considered yet (like implications on test automation etc.). Thank you!