Run MediaWiki unit tests via 'vagrant run-tests'

This patch uses extends the MediaWiki-Vagrant's Vagrant plug-in to add a
Vagrant subcommand, 'run-tests', that executes PHPUnit tests on a running VM.

With the exception of '-h' / '--help' (which prompt Vagrant to print usage info
and then exit), all other command-line arguments are passed through to phpunit.

This patch also fixes whitespace in other ruby files.

Bug: 46676
Change-Id: I7340a306d92ed5f4bb7cfb3c0a0a7b1e7c19fa53