Remove unnecessary pipeline::Value from SliceStore and SliceWriter

Compiles, but untested.
Move LocalStores to catmaid/persistence/local/
Move catmaid/django to catmaid/persistence/django
Moved checkDjangoError to DjangoUtils, check now throws an exception if it finds a problem
Django persistence: throw DjangoExceptions when something goes wrong on the server side
*SliceStore: throw an error if an attempt is made to store ConflictSets over Slices that are not already in the cache
moved writing of Segments to SegmentStore
Removed CoreSolver
binaries: updated wrt changes in catmaid persistence
Don't compile coresolvertest for now
pysopnet: remove references to deleted classes
Removed LocalSolutionStore