Improved build with grunt

I have changed the echo shell commands over to use the grunt.log API, and used subhead() to differentiate the output. It also wraps to 80 characters now, with proper word-breaking. With luck, the remaining grunt-exec should actually work on Windows too. (I don't have a computer to test it.)

Recent developments have negated the need for grunt-newer -- Boris, here, has made changes to the shared js so we don't need to compile it. Since compiling only takes a few seconds anyway, I don't think using grunt-newer is worth it now.

I will submit a new pull request.