Add rebuildGlossaryCache maintenance script

- Add rebuildGlossaryCache maintenance script "php rebuildGlossaryCache.php"
- Add SG\Tests\Maintenance\GlossaryCacheRebuilderTest
- Run tests using "php mw-phpunit-runner.php"

Change-Id: Ie45bc5bbbdf6db82c1f02dc32634f49972cc1237