Automation and miscellaneous improvements

compare_runs now also takes callables ...

... in addition to method names.

Cleanup automation.Problem class.

We remove the get_requires method and move it to SolveProblem. This de-links the Problem from anything PySPH specific. The generation of the tasks is now managed by the SolveProblem class and can be configured by the user if needed by passing a different class to the Automator.

Remove old enthought imports that mask real errors.

No one uses the ancient mayavi packages anymore which used enthought namespace packages. These would mask real import errors when users run pysph view. These are removed and should make it easier to debug such errors.

Create general purpose CommandTask.

• This makes it easy to use any command with the framework.

• PySPHTask subclasses this.

• Support user passing $output_dir in the command which is automatically replacedd.

• Added some simple tests for the new code.