Insert order into executable jar is not deterministic, causes classloading differences

[plaird]

We had some issues with classes being classloaded in a different order, depending on the platform that built the Spring Boot jar. We believe this is caused by the springboot rule packaging step not specifying the insert order into the spring boot jar between:

• spring boot loader
• BOOT-INF/classes
• BOOT-INF/lib

We want the order to be as depicted above.

[plaird]

PR #75 improved this feature such that the insert order of dependencies into the Spring Boot jar follows the BUILD file order. The documentation has the details:
https://github.com/salesforce/bazel-springboot-rule/blob/master/tools/springboot/unwanted_classes.md#classpath-ordering-using-the-build-file