WIP
Wip implementing ds_subtract/3
Another wip
Fixed coloring
Use ds_subtract to reason about intersections
Removed debug print
We need more colors if we also consider intersections.
WIP on repeating patterns
Merge branch 'master' of ct:projects/Spreadsheet

Conflicts:
	datasource.pl
Document latest work
Minor patches
Better modularity
Union of connected blobs
Experiment: get all labels
MODIFIED: ods_load/1 only loads if not already loaded.
WIP creating union of blocks