SliceGuarantor: Debug statements
SliceReader: sort slices before returning
LocalSliceStore: use std::map and such to preserver order
LocalSegmentStore: Sort retrieved segments before retrieval
Slice: Less-than operator over id's, for use with std::sort
Segments: Yell a lot if something that should never happen actually happens.
SegmentExtractor: Add some debug statements, and also do some changes that I'm not really sure what they do. Probably nothing.
Block: less-than operator for use as a key in a std::map
CoreSolver: Do constraint extraction right. This version seems to work in the trivial case, where a stack is covered by a single huge Block.
coresolvertest: minor changes