BUG: Fix copy s.t. it always copies index/columns.

Only copies index/columns with `deep=True` on `BlockManager`. Plus some
tests...yay! Change copy to make views of indices.

Requires changing groupby to check whether indices are identical, rather
than comparing with `is`. Plus add tests for name checks through
everything. Also, fixes tests to use `is_()` rather than `is`

CLN: Change groupby to use 'is_' instead
ENH: enable deep copy for sparse Series/Panel
CLN: PEP8 tests/test_index.py and core/index