`ComputationFrame`s replace old queries, breaking interface changes, simpler internals

This version:

• introduces ComputationFrame as the way to query storage
• makes a number of breaking changes and improvements, most important of which are:
  • any function can be decorated with @op now (no need for type annotations for outputs or a fixed set of inputs/outputs)
  • you can use just with storage: instead of with storage.run(): now
  • @op decorator supports output_names for named outputs
  • to make collection inputs/outputs of @ops transparent to the storage, use the custom type annotation constructors MList, MDict, ...
• rewrites and simplifies most of the memoization internals
• introduces a much more detailed documentation