    FDPanel object, a 4 dimensional pandas container (version 2)
FDPanel is like a Panel object, but provides 4 dimensions: labels, items, major_axis, minor_axis

(version 2: much of the code changes now occur in panel.py; fdpanel.py is a thin wrapper over an n-dim 
panel like obj; supporting NDPanel like objects with named higher dimension will be very easy)

instead of using a dict of Panels to hold data, the FDPanel provides a convenient represenation in pandas space
with named dimensions to allow easy axis swapping and slicing

see examples/4D Example 2.pdf for creation and usage
## motivation

io/pytables currently provides a nice representation of a table to store a Panel object
directly (assume item x major (dates) x minor)
FDPanel allows many named tables to represent a collection of these tables in a single hdf5 file
## testing

tests/test_fdpanel.py provides a similar methodology to test_panel.py

FDPanel required an overhall of many methods in panel.py and one change in core/index.py (regarding multi-indexing)
almost all methods in a Panel are extended to FDPanel (with the exception in that Panel now allows a multi-axis on axis 0)

docstrings need to be refreshed a bit and made a bit more general

all tests that are not skipped pass

join works but merge testing code not complete yet (pandas.tools.merge)
