[Pandas-dev] Reorganizing the megamodules

[Wes McKinney]

As part of improving our code organization, I'd like to look at
splitting up modules exceeding 3000 lines into subpackages. Obvious
targets are

core/frame.py
core/generic.py
core/index.py
core/series.py

For the "big" classes like Series and DataFrame, this amounts mainly
to having a common pattern for adding new instance methods that aren't
nested under the main class: header (or in one of their subclasses).

Thoughts?

- Wes