Do not install unnecessary dependencies

[carmocca]

Fixes #323
Fixes #278

Most of our dependencies are optional. Do not include them in our requirements.txt

[Andrei-Aksionov]

Don't know, maybe this question was asked before, but why does this repo uses only requirements.txt and not poetry. There is in-build functionality to separate essential and optional packages.
Given that PyTorch-Lightning uses poetry I assume that there should be a particular reason to not use it here. Maybe for simplicity?

[carmocca]

Yes, it's for simplicity