__init__.py:
- added handling for tuplets
- limiting returns to the Where clause is now optional
- extra validation for missing properties
- added missing _id() calls
- Query::music21Score() now starts only from Note objects
- _addHierarchicalNodes() returns only new objects
- added special ID property type to Property

musicNetServer.py:
- uses 10 GeneratePreviews workers instead of 1
- adapted prepareQuery() for new Where clause behavior
- queries now search for at most 1 score and 1 score/part relationship
- limited search results for multiple parts to 1 combination of parts
per set