Restructured torch modules to support shapr installation without torch (#393)

* Updated the mask generators

* Fixed the Neural Network Modules

* Fixed Dataset Utility Functions

* Added check that progressr is installed, otherwise we proceed without a progress_bar

* Fixed vaeac and memory layer

* Missed default value in `mcar_mask_generator`.

* Manuals

* Typos in the vaeac vignettes

* Updated the documentation to clearly state that a vaeac model cannot be moved from the folder it was trained in if one want to continue to train it. This is a limitation that I should consider fixing. But I am unsure how often this will occur.

Also made sure that continue train works if the explanation object was trained by giving a path.

* styler + lintr

* Added self as global variable