Bugfix and setup upgrades

Summary: Added nice Vagrant setup files. Removed HHVM known array_walk issue (#1935) in common/tags.php. Fixed round_update_task_list bug that was erasing all the tasks when database insert failure.

Test Plan: manual on localhost

Reviewers: adrian.budau, bogdan2412

Reviewed By: adrian.budau, bogdan2412

Subscribers: echipa-infoarena

Differential Revision: https://hackers.infoarena.ro/D31