-Nvidia OpenCL compilation was broken for density filtering due to ambiguity in the arguments to min(). Fix it by casting.
-Put Nvidia block size in DE back to 24 where it used to be. Nvidia fails when it's 32.
-Fix misspelling of the word "Rendering" in failure messages in final render dialog.
-Put FillSummary() back when loading an ember.
-Properly disable add final xform button when a final xform is present.
This adds a travis config to build everyting on 12.04. Because 12.04 is quite old, there are a certain number of hoops that need to be jumped through in order to get things working. As a result, the build script is more complex than I'd like.
