Fixup GWT Test runner

Add some logging, and enable the log console.
Only set dispose flag on ESC if a test is active.
Disable NetAPITest (it won't even compile because it abuses FileHandles).
Stub out Thread and Texture a bit more for GWT backend

Add a (working?) Thread.setUncaughtExceptionHandler.

Add a no-op setEnforcePotImages() on Texture.
Cleanup index.html for GWT test

Move body out of <head> and into <body>.  Add a bit of text explaining
what's going on and where its from.
Merge pull request #242 from bitiotic/gwtcleanup

GWT test cleanup