Updated the package graph in preparation for cleaning up the library.
Moved `Context`, `RuleLibrary`, and `OperatorLibrary` and supporting stuff into the new `context` package.  Expanded all `_` import statements and cleaned them up - except for gui and related packages.
Removed file stored in wrong place.
Rebuilt the compilable context stuff to better separate concerns, use the new package structure, and to create the context in stages.  Hopefully this will help with very large contexts.
Merge pull request #177 from sprowell/master

Refactoring.