Etna

Fixed
- Docs generation for neural networks

Changed
- Speed up `_check_regressors` and `_merge_exog` ([360](https://github.com/tinkoff-ai/etna/pull/360))

Fixed
- `Model`, `PerSegmentModel`, `PerSegmentWrapper` imports ([362](https://github.com/tinkoff-ai/etna/pull/362))
- Docs generation ([363](https://github.com/tinkoff-ai/etna/pull/363))
- Fixed work of get_anomalies_density with constant series ([334](https://github.com/tinkoff-ai/etna/issues/334))

Added
- ACF plot ([318](https://github.com/tinkoff-ai/etna/pull/318))

Changed
- Add `ts.inverse_transform` as final step at `Pipeline.fit` method ([316](https://github.com/tinkoff-ai/etna/pull/316))
- Make test_ts optional in plot_forecast ([321](https://github.com/tinkoff-ai/etna/pull/321))
- Speed up inference for multisegment regression models ([333](https://github.com/tinkoff-ai/etna/pull/333))
- Speed up Pipeline._get_backtest_forecasts ([336](https://github.com/tinkoff-ai/etna/pull/336))
- Speed up SegmentEncoderTransform ([331](https://github.com/tinkoff-ai/etna/pull/331))
- Wandb Logger does not work unless pytorch is installed ([340](https://github.com/tinkoff-ai/etna/pull/340))

Fixed
- Get rid of lambda in DensityOutliersTransform and get_anomalies_density ([341](https://github.com/tinkoff-ai/etna/pull/341))
- Fixed import in transforms ([349](https://github.com/tinkoff-ai/etna/pull/349))
- Pickle DTWClustering ([350](https://github.com/tinkoff-ai/etna/pull/350))

Removed
- Remove TimeSeriesCrossValidation ([337](https://github.com/tinkoff-ai/etna/pull/337))

Added
- RelevanceTable returns rank ([268](https://github.com/tinkoff-ai/etna/pull/268/))
- GaleShapleyFeatureSelectionTransform ([284](https://github.com/tinkoff-ai/etna/pull/284))
- FilterFeaturesTransform ([277](https://github.com/tinkoff-ai/etna/pull/277))
- Spell checking for source code and md files ([303](https://github.com/tinkoff-ai/etna/pull/303))
- ResampleWithDistributionTransform ([296](https://github.com/tinkoff-ai/etna/pull/296))
- Add function to duplicate exogenous data ([305](https://github.com/tinkoff-ai/etna/pull/305))
- FourierTransform ([306](https://github.com/tinkoff-ai/etna/pull/306))

Changed
- Rename confidence interval to prediction interval, start working with quantiles instead of interval_width ([285](https://github.com/tinkoff-ai/etna/pull/285))
- Changed format of forecast and test dataframes in WandbLogger ([309](https://github.com/tinkoff-ai/etna/pull/309))

Fixed

Changed
- Add sum for omegaconf resolvers ([300](https://github.com/tinkoff-ai/etna/pull/300/))

Changed
- Delete restriction on version of pandas ([274](https://github.com/tinkoff-ai/etna/pull/274))