Add support for behat_profiles and improved exit code for parallel runs

1. Exit code of parallel run is bit masked to reflect failed run.

1. Modify behat.yml and leave only 3 feature files.
2. Initialise behat with 3 runs. (php admin/tool/behat/cli/init.php -j=3)
3. Modify 1st and 3rd feature file so they fail.
4. Run parallel behat and check exit code. It should be 5 (php admin/tool/behat/cli/run.php) (echo $?)
5. Modify 2nd feature file, so it fails
6. Run parallel behat and check exit code is 7 (php admin/tool/behat/cli/run.php) (echo $?)

2. Test $CFG->behat_profiles and $CFG->behat_config

1. Set following in your config.php and ensure phantomjs and chrome profiles are set in behat.yml
2. Start runs with both --profile=phantomjs and --profile=chrome

   $CFG->behat_profiles = array(

   'phantomjs' => array(

   'browser' => 'phantomjs',

   'tags' => '~@_file_upload&&~@_alert&&~@_bug_phantomjs',

   'wd_host' => 'http://127.0.0.1:4443/wd/hub',

   'capabilities' => array(

   'platform' => 'Linux',

   'version' => 2.1

   )

   )

   );

   $CFG->behat_config = array(

   'chrome' => array(

   'extensions' => array(

   'Behat\MinkExtension\Extension' => array(

   'selenium2' => array(

   'browser' => 'chrome',

   )

   )

   )

   )

   );