Add EngineSource, EngineManager, and Mayavi2 plugin panel

[kitchoi]

Main features:

• [x] EngineSource for adapting CUDS from a simphony engine (analogous to CUDSFileSource)
• [x] EngineManager for selecting one modeling engines out of many (TraitsUI)
• [x] EngineManagerStandalone for visualising datasets from engine, running and animating the results (GUI-free)
• [x] EngineManagerStandaloneUI a GUI version of EngineManagerStandalone
• [x] EngineManagerMayavi2 as a panel to sit inside Mayavi2
• [x] EngineManagerMayavi2Plugin a envisage plugin for managing EngineManagerMayavi2
• [x] Added tests (except for EngineManagerMayavi2)
• [x] Added documentation
• [ ] Tests for EngineManagerMayavi2

Supporting elements:

• [x] AddEngineSourceToMayavi, AddSourcePanel, RunAndAnimate and RunAndAnimatePanel (for reusability)
• [x] TabbedPanelCollection collects multiple panels and displays as tabs
• [x] default_modules for setting default mayavi modules given the point_scalars_name/... (also see changes in show.py)

[dpinte]

@kitchoi great work! See my comments in the code

[kitchoi]

@dpinte Thanks for reviewing the code! I have:

• added trait's tests (traits.testing.UnittestTools) for EngineManager, AddSourcePanel and EngineManagerStandaloneUI (AddEngineSourceToMayavi and RunAndAnimate are not subclasses of HasTrait)
• kept the __init__ for EngineManagerStandaloneUI for it to be consistent with EngineManagerStandalone
• __init__ in AddSourcePanel, RunAndAnimatePanel and TabbedPanelCollection are removed.
• replaced logging.warn/info/.. with logger.warn/info/...
• added more tests for default_module

Forgot to ask, is it possible to test EngineManagerMayavi2 and EngineManagerMayavi2Plugin as it is being loaded by envisage?

[kitchoi]

@dpinte is this good to merge?

As for loading engine wrappers from *.py file or from default factory function, I am planning to put this into a separate PR:

[dpinte]

@kitchoi LGTM. And a separate PR for the latest additions is definitely a good idea

[kitchoi]

Thanks!