Add support for publication size weighting. General refactoring of IB…

…MA estimators (#887)

* Refactor Stouffers, and support  publication size weighting

* Remove raw_data to save memory

* Refactor Fishers

* Refactor WeightedLeastSquares

* Refactor DerSimonianLaird

* Update ibma.py

* Refactor _fit()

* Refactor Hedges

* Refactor SampleSizeBasedLikelihood

* Refactor VarianceBasedLikelihood

* Refactor PermutedOLS

* Update ibma.py

* Update new parameter in reports

* Major refactoring of IBMA estimators

* Add test for use_group_size

* Test Stouffers correction with multiple contrast

* Fix lint

* Rename variables