[WIP][ENHANCEMENT] added methods to retrieve portals and urls from WebspaceManager

__Tasks:__

- [x] test coverage
- [ ] gather feedback for my changes


__Informations:__

| Q             | A
| ------------- | ---
| Tests pass?   | yes
| Fixed tickets | none
| BC Breaks     | none
| Doc           | none
You don't seem to do anything with these parameters.

In anycase, I would be more tempted to do

````
class EnvironmentNotFoundException extends PortalException
{
}
````

and manually pass the message:

````
throw new EnvironementNotFoundException(sprintf('The environment "%s" for portal "%s" has not been found',
    $environment, $portal->getName()
);
````
In the code unless that *exact* sitation happens more than once.