Add command to poll github for new commit

If you have a server that is not accessible for github, you can't use webhooks to automate the builds. I've created a command that will poll github for the latest commit id and start the build if it's different from the last one.

To use this command, add the following line in your crontab:
 *      *   *   *   *     /usr/bin/php /var/www/tools/PHPCI/console phpci:poll-github

Also added a little error catching when saving project settings