Merge pull request #651 from NNPDF/add-data-kw

doc/sphinx/source/vp/dataspecification.rst

doc/sphinx/source/vp/index.rst

doc/sphinx/source/vp/theorycov/examples.rst

n3fit/src/n3fit/io/reader.py

validphys2/src/validphys/checks.py

...dphys2/src/validphys/comparefittemplates/comparecard.yaml

validphys2/src/validphys/comparefittemplates/report.md

validphys2/src/validphys/config.py

validphys2/src/validphys/core.py

validphys2/src/validphys/dataplots.py

validphys2/src/validphys/filters.py

validphys2/src/validphys/fitdata.py

validphys2/src/validphys/kinematics.py

validphys2/src/validphys/loader.py

validphys2/src/validphys/results.py

...hys2/src/validphys/tests/regressions/test_datasetchi2.csv

...dphys2/src/validphys/tests/regressions/test_expcovmat.csv

...s2/src/validphys/tests/regressions/test_expsqrtcovmat.csv

...rc/validphys/tests/regressions/test_no_regularization.csv

.../validphys/tests/regressions/test_pdf_plus_exp_covmat.csv