Define, annotate and document what belongs to the public API

[sebinside]

With release 4.0.0 in sight, we shall clearly define which JPlag interfaces belong to the public API and thus require changing the version numbers in the future, according to semantic versioning.

Potential interfaces are:

• The Java API (definitely a public interface)
• The CLI (probably also a public interface)
• The interface between the core and languages API (for the near future a private interface)
• The interface/file format between JPlag and the report viewer (probably also a private interface)

Also, we should then mark all methods that belong to the public API, e.g., by using java annotations. This shall minimize the risk of accidentally breaking semantic versioning for future versions.

[tsaglam]

With v6.0.0 (currently in planning), we will move to the local-mode-only version of JPlag, meaning JPlag will host the report viewer locally and launch it in the browser automatically. Thus, the JSON serialization between the report viewer and JPlag core is no longer considered public API.