ilastik/applets/base/appletSerializer.py: Added the conversion of a given roi to a slicing for SerialBlockSlot.
Merge pull request #1026 from jakirkham/roi_to_slicing_SerialBlockSlot

Fix for handling rois in SerialBlockSlot
serializer: Always read group names in numerically sorted order, even if the name isn't formatted with leading zeros.
serializer: Added an assertion for expected slot type in SerialBlockSlot constructor
Merge branch 'master' of git://github.com/ilastik/ilastik
Passing labels to the constructor only.