KTX support

This is the initial code for adding KTX loading support. I am still in the process of writing a tool to convert the existing texture files but I needed to push this to my repo for build testing anyway, so I may as well make the request now as well.  I can confirm successful build in Windows (see my wonderfully done [test screenshot](http://imgur.com/7xeHjKj)) but am still in the process of testing in my linux systems, but I see no reason  that it wouldn't work. I was also unable to add lib binaries for OSX since I don't use it.

This fixes #97