Include paths are processed from left to right, so we use Prepend to
ensure that paths to bundled thirdparty files will have precedence over
system paths (e.g. `/usr/include` should have lowest priority).
-Improvements to texture importer
-Proper detection of S3TC compression modes, and added all modes to Image
-Fixes to non-power of 2 compressed textures, which should all be supported by GLES3