There are four assistant roles:

creator (``crt`` in short)
  creates new projects
modifier (``mod`` in short)
  modifies existing projects
preparer (``prep`` in short)
  prepares environment for development of upstream projects
task (``task`` in short)
  performs arbitrary tasks not related to a specific project

The main purpose of having roles is separating different types of tasks.
It would be confusing to have e.g. ``python django`` assistant (that
creates new project) side-by-side with ``eclipse`` assistant (that registers
existing project into Eclipse).
