EVs

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.

dimensionality

changed data.

identifying reference image associated with a FIRST vtk file.

space as another.

and hashbang into every .py file.

path looks like part of an incomplete file group.

when called programmatically.

programmatically invoked.