Remove obsolete metatransformer submodule

[gtauzin]

Types of changes Remove deprecated metatransformer

Description Remove metatransformer submodule and its documentation

Any other comments? The metatransformer submodule was meant to be a simple sklearn compatible way of generating tda features. However, its transformers are now:

• harder to understand: the documentation is large and does no longer match the standard of quality of the rest of the code
• harder to maintain: a change in the documentation or in the api of one of its transformer will make them unusable
• incompatible with sklearn: they do not return a 2d array and are therefore not usable in standard machine learning pipelines, which makes them pointless
• unflexible: They are all based on VietorisRips and work only on point clouds while their name makes the user assume that they can take as arguments any data type.
• obsolete: They are not being maintained anymore

Checklist

• [x] I have read the guidelines for contributing.
• [x] My code follows the code style of this project. I used flake8 to check my Python changes.
• [x] My change requires a change to the documentation.
• [x] I have updated the documentation accordingly.
• [x] I have added tests to cover my changes.
• [x] All new and existing tests passed. I used pytest to check this on Python tests.

[ulupo]

/azp run

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