Prepare formal Qt for Android's Java API review

Following C++ API review rounds, and because of the QML embedding into native Android apps, the Java APIs, will be more exposed to users. Thus, to keep changes in check, do steps to start a formal API review round for Java.

This would ideally mean having a script(s) that makes the process automated, that would eventually live under qtqa/scripts/api-review.

I've looked into javap and javadoc tools for generating public API changes that can then be used to generate a diff. javadoc seems more promising because it would include the actual docs changes and not only the high level declarations that's generated with javap. Using javadoc Doclet API it might be possible to create a custom format like Markdown instead of the default HTML format.