these return 3D images with the binary or probabilistic mask
in a new image.Image with the name set to the label name
and the same NIFTI header as the atlas

makes the output

files have int type, which they don't. Also atlases handles spaces in XML
specifications

related code in atlas classes

into the AtlasDescription.labels list.

in the same space as the atlas. This might change in the future.

longer returned by anything - only label values (i.e. volumeindex + 1) and
proportions are returned.

labels than in the description (the striatum ones).

weighted mean correctly.

adjusted resample method to force float output (although this might change).

featdesign.loadDesignMat function

returning/assuming transposed affines (column-major). This is because that's
what OpenGL uses.

0. AtlasRegistry is no longer thread-safe. It was causing too much
   trouble, and loading atlas descriptions is not a bottle neck anyway,
   so it's completely unnecessary.

1. AtlasDescriptions are now stored as a sorted list.

2. All atlases (including those in $FSLDIR) are saved.

3. More AtlasRegistry methods to rescan, check, and remove atlases.

Little bugfix in Notifier - calling skip/enabled methods with no listeners
registered would result in error.

previous commit.

habit of calling it mutliple times from different threads. Some updates
to AtlasDescription class - am intending to allow users to select
atlas resolution.