pandas needs a package-wide config object?

I'm working on the next Unicode PR, which incorporates some global configurables,
and I can't seem to find a convention for handling that uniformly in pandas.

format.py has _GlobalPrintConfig/print_config, and core.api has the corresponding
set_printoptions, It looks to me like they need to be integrated into something more general.

Examples from other projects:

• matplotlib has rcParams
• IPython does things differently with config.configurable , but still has a well defined way of
  using/adding configurables.

I suggest a new core.config module to hold all configurables,
It will take over print_config (set_printoptions will keep working),
but will provide a more general namespacing scheme for configurables along with a
getter/setter to be added to core.api.

Once the getter/setter convention is put into place and used uniformly in the code,
the underlying implementation can change as necessary when pandas grows.

if this sounds reasonable, I can follow up with a PR. @wesm?

[wesm]

This seems perfectly reasonable. I expect there will be more and more configuration options as time goes on.

closed via 3f6e316