Added
- Core operations of tensor algebra
- Classes for different tensor representations (`Tensor`, `TensorCPD`, `TensorTKD`, `TensorTT`)
- Functions for computing special types of tensors (`super_diag_tensor`, `residual_tensor`)
- Implementation of the most fundamental tensor decompositions (`CPD`, `HOSVD`, `HOOI`,`TTSVD`)
- Several methods for computing metrics of tensor decompositions
- Functions for estimating optimal Kruskal rank and computing multi-linear rank of a `Tensor`