Essentials Plugin SDK

We want to offer an Essentials plugin SDK to 3rd parties, in order to help them create Essentials plugins.

The SDK consists of the following parts:

1 A stable and documented plugin descriptor structure.
2 An SDK JAR with a stable API, providing utilities and interfaces for the back-end part of an Essentials plugin to interact with the Essentials core functionality.
3 A stable and documented front-end API, providing functionality to the front-end part o fan Essentials plugin to interact with the Essentials dashboard.

We consider the following aspects of the SDK important: terminology should as much as possible be self-explanatory / self-documenting. This includes the names of artifacts, packages, classes, methods etc.. We try to limit the amount of documentation to the necessary minimum, focusing on showing how to achieve certain (frequently used) things. We intend to revisit and document the swagger UI as a means to document a part of the front-end API (3). We strife towards a minimal first version of the SDK JAR (2). Additional functionality can be added in the future. All pieces of the SDK are supposed to be peer-reviewed for optimal quality.