Requirements installation

[dilyararimovna]

Hello!

Now installation of additional requirements can be done either through python -m deeppavlov install <config-name> or pip install -r DeepPavlov/deeppavlov/requirements/fasttext.txt. This variant is not appropriate when you installed library with pip and trying to use it from python.

So, it would be nice to make the following:
python -m deeppavlov.requirements shows available requirements,
python -m deeppavlov.requiremets tf-gpu spacy gensim installs additional listed requirements from corresponding files in DeepPavlov/deeppavlov/requirements/ folder.

Thank you in advance.

[IgnatovFedor]

Turned out to be relevant because of the python pipelines