[REF] Move remaining locale functions to _config.localization
There are a a couple locale-centric functions left in `tm` that have not yet been moved because they depend on `pd.options.display.encoding`.  This PR implements a minimal `_config.display` that allows us to consolidate the locale functions.  `_config.display` also defines `display.date_dayfirst` and `display.date_yearfirst`, since those are used by `tslibs.parsing`.  So this completes the process of removing `tslib`'s dependency on `core`.

The existing `get_locales` function has a `if PY3` check that is no longer necessary, so this removes the PY2 branch of that.