RF: remove coordmap argument to image.fromarray

The argument didn't make much sense because if you have a coordmap
already, ``Image(data, coordmap)`` is the right way to create the image.

Closes gh-30.
DOC: update docstring for fromarray

Specify that identity affine maps input to output.
NF - Image.from_image classmethod

Trivial in its current state, but it may be useful for subclasses of
image with different __init__ semantics.
RF: use coordinate map product to append affines

I was using a kludgy append_diag routine put into nibabel for expanding
the input and output dimensions of an affine transform.  Jonathan
pointed out that ``product`` does this.
ENH: FDR - catch having NaNs, faster pth_from_pvals

new:
In [28]: %timeit FDR().pth_from_pvals(all_data_p, 0.05)
100 loops, best of 3: 14.3 ms per loop

old:
In [14]: %timeit FDR().pth_from_pvals(all_data_p, 0.05)
10 loops, best of 3: 57.2 ms per loop
Merge pull request #160 from matthew-brett/consistent-fromarray

RF: clean up image.fromarray

Remove CoordMap argument to fromarray; it didn't make much sense because if you have a coordmap already, Image(data, coordmap) is the right way to create the image.
DOC: typos, fixes, formatting for image docstrings

There should be no functional change in doctests or code.
NF - add is_coordsys CoordinateSystem check

With tests.
NF - allow coordinate names for coordinate system

In creating a coordinate map, allow coordinate names as definitions for
the two coordinate systems, making an easier shorthand for coordinate
map creation.
DOC: fixup io docstrings, remove mention of fromarray

Remove mention of fromarray.  Cleaup some text, comments and whitespace
RF - replace use of fromarray in doctests/examples

Replace 'fromimage' with full Image construction syntax.  Why?  Because
it ellides past the need for the image to have a meaningful transform,
and because it's not much simpler (any more) than using the
AffineTransform constructor.

The examples here were broken in various ways, and run with these
changes.
NF - deprecate fromarray; update dostrings

fromarray not generally a good idea because it does not specify a
mapping; deprecate, remove mention in docstrings.
NF - rename default xyz axes with explicit labels

Instead of 'mni-x', 'mni-x=L->R' etc.
NF - add unknown and aligned output coordsystems

To be able to support range of nifti transform codes.
NF - XYZSpace class to make, test coordsys-likes

XYZSpace class allows us to check if a coordinate system, or a
coordinate map, or an Image (that has a coordinate map) are 'in' a
particular space - meaning - they have 'x', 'y', 'z' space names in the
right order.
RF - rename CoordmapMaker voxel_cs to voxel_csm
NF+RF - get axis names / output spaces from images

Discard affine_transform_from_array function that Jonathan had marked
for future deletion.

Implement reading of nifti dim_info to get phase, frequency, slice
labels from nifti header when available.

Read sform and qform information from nifti header to set output space.
Use standard 'unknown' xyz output space as default.

Add tests.
NF - add spaces to nipy.core.api imports

MNI etc spaces may be useful at the API level
RF: contains space check allows axes in any order

Previously contains would check if the axes for the checked object were
in the exact order of the space against which it was being checked.
That meant that, if we roll time first for an MNI space image, it would
no longer be `in` MNI space. With these changes, the image continues to
be in MNI space, but cannot - for example - generate an xyz affine
without rearrangement.
NF: add test for xyz space API

Allows check whether this is an XYZ space definition.