WIP: thesaurus using DocumentFeature-s internally instead of str to avoid the need to convert back and forth during lookups from a PredefinedNeighbours vector source (which takes a very long time)
Thesaurus using DocumentFeature-s internally instead of str to avoid the need to convert back and forth during lookups from a PredefinedNeighbours vector source (which takes a very long time). All returned neighbours are also DocumentFeature-s. This avoids performing multiple expensive convertions to and and from (especially from) string to a DocumentFeature
Added a few more things to discoutils to match thesisgenerator's requirements
Enabled shelve writeback to have it cache results and reduce disk reads. This considerably speeds things up.