Restored setBuildVersion.sh script and modified it to set CFBundleVersion...

... to the git commit SHA for only Debug builds.

As requested by @bbodenmiller in #233, I restored the build phase run script. Before submitting to the App Store @caitbonnar will need to set CFBundleVersion to a valid version number. After submitting, CFBundleVersion should be reverted to the preprocessor definition: GIT_COMMIT_SHA.