Allow arbitrary texture size

Other:
-added image size constants to TextureCombiner
-TextureFunctions now use width and height parameters
-TextureFunctions.generate() scales by constant 256 instead of parameter
-Java template now creates a nice big 600x400 image
Added Export Code to Scala

Other:
-renamed "Export" to "Export Code"
-updated tutorial pages
-fixed minor typo in TemplateJava.txt
Merge pull request #20 from skiyooka/master

Two pieces