feature #14198 Automatically start server:run if server:start failed (WouterJ)
feature #14198 Automatically start server:run if server:start failed (WouterJ)

This PR was merged into the 2.7 branch.

Discussion
----------

Automatically start server:run if server:start failed

After this PR, `server:start` will ask the user if it wants to start `server:run` automatically. If yes, the `server:run` command is executed and the server is started. If no, the command exits with `1`.

Example of Yes:
```
$ php app/console server:start
This command needs the pcntl extension to run.
You can either install it or use the server:run command instead to run the built-in web server.
Do you want to start server:run immediately? [Yn]
Server running on http://127.0.0.1:8000

Quit the server with CONTROL-C.
```
Example of No:
```
$ php app/console server:start
This command needs the pcntl extension to run.
You can either install it or use the server:run command instead to run the built-in web server.
Do you want to start server:run immediately? [Yn] n

$ ...
```

I've created this PR, because documentation currently still has to promote `server:run` to be safe. You don't want to tell people, "use `server:start`" and have them getting an error immediately (please note that starting the server is probably the first action with Symfony). Example: https://github.com/symfony/symfony-demo/pull/17

| Q             | A
| ------------- | ---
| Bug fix?      | somewhat
| New feature?  | somewhat
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

Commits
-------

f95d89c Automatically start server:run if server:start failed

symfony/framework-bundle