Removed Java 1.7 dependencies from source. Now only requires 1.6. Changes made to support building on OS X 10.6. Bundled library lib/appbundler-1.0.jar still requires 1.7 but flightplot.jar can still be build with target "flightplot" and run with the usual "java -jar /path/to/flightplot.jar".
Merge pull request #1 from pigeonhunter/master

Java 1.6 support, for Snow Leopard users.