MDL-39752 behat: Modified following for parallel run:
1. Create behat datadir within behat_dataroot not at same level 2. Define suffix for link and not use hard-coded values 3. Renamed ns_parallel to run.php 4. Rename variables to best understand them 5. Added support for each run to specify db, prefix, rerun and profile. 6. Showing number of steps in each line of parallel run.