Commit to replicate OOPLSA 2021 'Compilation of Sparse Array Programm…

…ing Models'

For reproducing results in the OOPSLA 2020 paper "A Sparse Iteration …

…Space Transformation Framework for Sparse Tensor Algebra" https://doi.org/10.1145/3428226

Various fixes including better temporary inserts

Adds IndexNotationVisitors

The version of taco described in the paper "The Tensor Algebra Compil…

…er" at OOPSLA 2017.