Refactoring the SDK structure to be more discoverable

[Tanz0rz]

This is a large refactor of the overall structure to achieve two things:

1. The code itself needed to be more discoverable for someone trying to understand how it works by browsing the project.
   • All non-required files were moved from the client package to the internal package to limit the noise when looking through the code
   • Methods that directly mapped to API endpoints were updated to match the underlying API path as closely as possible
2. The docs were updated to simplify and streamline compiling an example program that uses the SDK
   • The development notes were moved to a DEVELOPMENT.md file
   • A LICENSE.txt file was added (and will be filled out soon)
   • The README.md was simplified
   • A CHANGELOG.md file was added to summarize the development of the project and link to all tagged releases
     • A top-level changelog was added to the project root which will link to all SDK changelogs