Better handling of JRE on OSX

The stub Java that exists when no JRE is installed appears in all the right paths, so perform the same check the Oracle JRE install does against the bundle identifier.

In the launchd plist, set the JAVA_HOME environment variable to the install location that was confirmed. This is required as the JRE-only install doesn't update /usr/bin/java.

Lastly, fdbsqllayer had support for JAVA_HOME already but it wasn't space safe. Add some quotes.

Minor data_path tweak, for when Persistit is running, to be consistent with all other installs (i.e. subpath of data).