Support third party packages

Support a third party ecosystem where others can create packages for Objo that can be imported into a project easily from the IDE. The system should support open- and closed-source packages.

A closed-source package should let a developer distribute reusable classes, modules, and related components that another Objo Studio user can compile and run without being able to view or edit the implementation source. One concrete use case is a contractor handing a client the rest of a project's source while retaining proprietary implementation code in a supplied package.