There are times when an user will need to interactively extend a task workflow by
adding new tasks or a pre-connected set of tasks to the existing workflow, including
new dependencies and adaptors.  To provide this functionality, SMTK adds  the concept
of a *worklet*.  A *worklet* is an object representing a set of tasks created to
reuse a set of workflow logic in multiple workflows. In SMTK, a worklet is represented
as a component of a project and is managed by a project's task-manager in a collection
of worklets known as the "gallery."

This change also
+ makes `task::Adaptor` inherit `resource::Component`
+ refactors task events and their observers to occur during observation
  of operation results (rather than spontaneously, since now that tasks,
  adaptors, and worklets are components, that would force these events
  to happen during operations).
+ adds a simple worklet example in the data/projects directory called
  SimpleWorkletExample.
+ moves the `math_op.py` ...