[otrs] I converted all the png images to indexed mode

Hi everyone I have converted all the png images to indexed mode so they show up transparant in internet explorer. Internet explorer cannot display png's trasparant when in RGB mode. This will be of interest to anyone who has a non white background for the images. There were a couple images that just had white background which I converted to transparant as well. I did not check out the customer facing icons, if someone wants to let me know if they look fine let me know.