Fix issue #1 and introduce schema updates

* renamed some log columns: `http_get`, `http_post` and `http_server`
* added schema update command `./app/console lexik:monolog-browser:schema-update`

The default behavior of `lexik:monolog-browser:schema-update` could sometimes be not perfect, like on renaming columns because Doctrine don't manage them well (drop column and create a new one), so you may install Doctrine Migrations on your project. You have to generate a new migration class with this command `./app/console doctrine:migrations:generate` and for the MySQL platform feel free to get the example code below and to adapt it to your own needs:

```php
<?php

namespace Application\Migrations;

use Doctrine\DBAL\Migrations\AbstractMigration;
use Doctrine\DBAL\Schema\Schema;

use Symfony\Component\DependencyInjection\ContainerAwareInterface;
use Symfony\Component\DependencyInjection\ContainerInterface;

class Version20130625221051 extends AbstractMigration implements ContainerAwareInterface
{
    private $container;

    public function setContainer(ContainerInterface $container = null)
    {
        $this->container = $container;
    }

    public function up(Schema $schema)
    {
        $tableName = $this->container->getParameter('lexik_monolog_browser.doctrine.table_name');
 
        $this->addSql(sprintf('ALTER TABLE `%s` CHANGE `server` `http_server` LONGTEXT NOT NULL ;', $tableName));
        $this->addSql(sprintf('ALTER TABLE `%s` CHANGE `post`   `http_post`   LONGTEXT NOT NULL ;', $tableName));
        $this->addSql(sprintf('ALTER TABLE `%s` CHANGE `get`    `http_get`    LONGTEXT NOT NULL ;', $tableName));

    }

    public function down(Schema $schema)
    {
        $tableName = $this->container->getParameter('lexik_monolog_browser.doctrine.table_name');

        $this->addSql(sprintf('ALTER TABLE `%s` CHANGE `http_server` `server` LONGTEXT NOT NULL ;', $tableName));
        $this->addSql(sprintf('ALTER TABLE `%s` CHANGE `http_post`   `post`   LONGTEXT NOT NULL ;', $tableName));
        $this->addSql(sprintf('ALTER TABLE `%s` CHANGE `http_get`    `get`    LONGTEXT NOT NULL ;', $tableName));
    }
}
```