From release notes: PackMan: In 2017.2, we are introducing Unity Package Manager. This will be the first stepping stone for the system. We are taking an incremental approach to integrate the system into the Unity ecosystem. It will grow with more features over time. For this first release, we avoid exposing user facing features. Instead, we are exposing an API for enabling internal components to be updated more frequently than the editor (the first pillar of the system). What is it's purpose?