All classes have moved to BEAST 2 (>= v2.6.6) and BEASTLabs (>= v1.9.7).
The outercore package of BEAST 2 has core features, not in the core :)
It is also released as a BEAST 2 package. How to install and use BEAST 2 packages can be seen here.
This project requires Java 1.8.