Consider vectorised versions of hypervector functions

[rgayler]

The currently defined (bipolar) functions have single hypervectors as the arguments and outputs.
Consider whether it would be useful to generalise these functions to work with collections (lists or vectors) of hypervectors.

The VSA_altitude_hold::run_simulation() function returns a data frame with list columns of hypervectors.

Torchhd generator functions return arrays of hypervectors (tensors), presumably fro compatibility with pytorch.

List columns of hypervectors are probably more idiomatic for R analyses, but it might eventually be useful for this package to be based on tensorflow for performance, in which case a tensor representation might be needed.