Jenkins build cleanup

This accomplishes a few things

* allows build.xml to be used to build the Launcher app from the command line
* if xcodebuild fails, the entire build fails
* displays the status of the last build in the README

Don't be surprised that the build says it is failing currently, since upgrading the machine that the build is running on, Xcode thinks that it needs a user to complete the signing of the app. I am working on fixing that.

(I didn't have permission in github to push directly to develop so I figured I would just send this as a pull request, plus it gave me the opportunity to mention the thing about the README in a place where hopefully people will see it, you can even take a look at it [here](https://github.com/datalogics-bhaugen/SDKLauncher-OSX/blob/jenkins-build-cleanup/README.md) as a preview)