This PR was merged into the 2.5-dev branch.Discussion----------[Console] A better progress bar| Q             | A| ------------- | ---| Bug fix?      | no| New feature?  | no| BC breaks?    | no| Deprecations? | no| Tests pass?   | yes| Fixed tickets |#9573,#9574,#10187,#9951, related to#9788| License       | MIT| Doc PR        |symfony/symfony-docs#3626TODO: - [x] add some docsSee what this PR allows you to do easily:![cwzpvk](https://f.cloud.github.com/assets/47313/2302190/30cd80e4-a170-11e3-8d88-80c4e4ca8b23.gif)## New ProgressBar classFirst, this PR deprecates `ProgressHelper` in favor of `ProgressBar`. The main difference is that the new `ProgressBar` class represents a single progress bar, which allows for more than one bar to be displayed at a time:```phpuse Symfony\Component\Console\Helper\ProgressBar;use Symfony\Component\Console\Output\ConsoleOutput;$output = new ConsoleOutput();$bar1 = new ProgressBar($output, 10);$bar2 = new ProgressBar($output, 20);$bar2->setProgressCharacter('#');$bar1->start();print "\n";$bar2->start();for ($i = 1; $i <= 20; $i++) {    // up one line    $output->write("\033[1A");    usleep(100000);    if ($i <= 10) {        $bar1->advance();    }    print "\n";    $bar2->advance();}```And here is how it looks like when run:![progress-bars](https://f.cloud.github.com/assets/47313/2300612/4465889a-a0fd-11e3-8bc2-b1d2a0f5dc3d.gif)## Format PlaceholdersThis pull request refactors the way placeholders in the progress bar are managed. It is now possible to add new placeholders or replace existing ones:```php// set a new placeholderProgressBar::setPlaceholderFormatterDefinition('remaining_steps', function (ProgressBar $bar) {    return $bar->getMaxSteps() - $bar->getStep();});// change the behavior of an existing placeholderProgressBar::setPlaceholderFormatterDefinition('max', function (ProgressBar $bar) {    return $bar->getMaxSteps() ?: '~';});```Several new built-in placeholders have also been added: * `%remaining%`: Display the remaining time * `%estimated%`: Display the estimated time of the whole "task" * `%memory%`: Display the memory usage## FormatsFormats can also be added (or built-in ones modified):```phpProgressBar::setFormatDefinition('simple', '%current%');$bar->setFormat('simple');// is equivalent to$bar->setFormat('%current%');```Built-in formats are: * `quiet` * `normal` * `verbose` * `quiet_nomax` * `normal_nomax` * `verbose_nomax`## Format MessagesYou can also set arbitrary messages that depends on the progression in the progress bar:```php$bar = new ProgressBar($output, 10);$bar->setFormat("%message% %current%/%max% [%bar%]");$bar->setMessage('started');$bar->start();$bar->setMessage('advancing');$bar->advance();$bar->setMessage('finish');$bar->finish();```You are not limited to a single message (`message` being just the default one):```php$bar = new ProgressBar($output, 10);$bar->setFormat("%message% %current%/%max% [%bar%] %end%");$bar->setMessage('started');$bar->setMessage('', 'end');$bar->start();$bar->setMessage('advancing');$bar->advance();$bar->setMessage('finish');$bar->setMessage('ended...', 'end');$bar->finish();```## Multiline FormatsA progress bar can now span more than one line:```php$bar->setFormat("%current%/%max% [%bar%]\n%message%");```## Flexible Format DefinitionsThe hardcoded formatting for some placeholders (like `%percent%` or `%elapsed%`) have been removed in favor of a `sprintf`-like format:```php$bar->setFormat("%current%/%max% [%bar%] %percent:3s%");```Notice the `%percent:3s%` placeholder. Here, `%3s` is going to be used when rendering the placeholder.## ANSI colors and EmojisThe new progress bar output can now contain ANSI colors and.or Emojis (see the small video at the top of this PR).Commits-------0d1a58c [Console] made formats even more flexible8c0022b [Console] fixed progress bar when using ANSI colors and Emojis38f7a6f [Console] fixed PHP comptability244d3b8 [Console] added a way to globally add a progress bar format or modify a built-in onea9d47eb [Console] added a way to add a custom message on a progress bar7a30e50 [Console] added support for multiline formats in ProgressBar1aa7b8c [Console] added more default placeholder formatters for the progress bar2a78a09 [Console] refactored the progress bar to allow placeholder to be extensible4e76aa3 [Console] added ProgressBar (to replace the stateful ProgressHelper class)