Update oswelcome.php

Added new background image rotation jquery thingy, just create a folder, drop your grid's screenshots in that folder then put the name of that folder in $dir of this page and BAM new pic every 5 seconds for your users to see of your grid while they input their login information. Still kinda buggy which i will fix soon. Enjoy.
Merge pull request #1 from chrisx84/master

Update oswelcome.php