Write API Documentation in Wiki

Hey all,

Treasury has recently released it's Version 2 update and requires a full Wiki refresh. At the moment, all that is left to write is the API documentation. All of Treasury's APIs have javadocs, so writing the Wiki should be a trivial matter of explaining core concepts and giving examples on how to use the APIs for common requirements. Our core development team have spent a lot of time designing and writing the code and would greatly appreciate community contributions to finish the Wiki.

If you're interested in helping out, the Wiki pages have been set so anyone can edit them - please feel free to get started and leave a comment if you have any questions.

The following Wiki pages are outdated as of the recent API revisions in Treasury v2, and we wish to address them in this issue.

- [ ] [Economy API](https://github.com/ArcanePlugins/Treasury/wiki/Treasury's-Economy-API)
- [ ] [Services API](https://github.com/ArcanePlugins/Treasury/wiki/Treasury-Services-API)
- [ ] [Events API](https://github.com/ArcanePlugins/Treasury/wiki/Treasury-Events-API)

The first API documentation page I recommend we focus on at the moment is the [Economy API](https://github.com/ArcanePlugins/Treasury/wiki/Treasury's-Economy-API), which will be the most content-heavy of them all. This page will not only need to describe the API's features (as it currently does but for the previous API revision), but also *how* to use each feature. The same type of content and layout should follow with the other API pages.

Documentation contributions will be officially recorded in the Credits page and this may be useful if you would like to contribute to open-source projects for your resume.

Thanks!

Start with the Economy API wiki page and compare its content with Treasury v2's JavaDocs, focusing on core concepts, features, and common-use examples. Then apply the same documentation approach to the Services API and Events API pages; done means all three outdated wiki pages describe the v2 APIs accurately.

Written by the indexing model from the issue text.