Taking out Catboost model from SkLearnEvaluationStrategy into separate Boosting class strategy.

New features for CatBoost:

Converting data into Pool;
Fitting with eval_set, early_stopping_rounds and best_model;
Defining categoricat features for model;
Ploting features importances;
Saving/Loading model (required for implementation in Bagging method implementation to FEDOT #1005);
Updated search space.
Updates in data, preprocessing and data_split:

Storing not encoded categorical features (into OHE or LE) and using it where necessary;
Storing positions for different types of data (numeric, category and encoded);
Storing features names of dataset.

* added warning tracking during building documentations
* updated requirements dependences up to late 
Co-authored-by: Denis Sidorenko <sidorenko.den95@gmail.com>

* Docstrings and docs refactored

improved RTD structure
Co-authored-by: Denis Sidorenko <sidorenko.den95@gmail.com>

simplified requirements setup according to the needs

* Add new structure of README

* Add How to use section in README

* Fix typo in README

* Add links to examples in How to use

* Update README.md

* Abstract extended

* add README.rst

* fix .rst && rename old README

* fix license link

* fix indents

* fix example links

* Update README.rst

* Test readthedocs via push

* add index.rst && .readthedocs.yml

* add config via sphinx

* fix docs config

* remove readthedocs.yml

* add theme

* remove redundant files

* add Basic Concepts

* fix mistakes

* Fix typo in how-to-use section

* Update installation in README

* Update README.rst

Contribution and citation added

* contributing.md added, readme ipdated

* Papers added

* Contributing renamed to rst, links fixed

* TPOT/H2O-related tests excluded

* Req.txt changed to full

* add sphinx

* fix master_doc

* add remaining docs

* add tuning api, full info documentation

* move default log file, fix tuning.rst

* fix tuning.rst

* fix autodoc inheritance

* main objects docstrings

* add type hints ext

* fix docs reqs

* use apidoc

* add Data docstring

* add rtd config

* fix config

* add mock

* add more mock

* add bysource

* customized version

* docs contribution

* Fix typos in contributing.rst

* Fix typos

* Fix typos

* Update project structure in README