Merge branch 'master' into sketch-map

CHANGES/v2.3.md

CHANGES/v2.4.md

CHANGES/v2.5.md

regtest/basic/rt66dna/1bna.gro

regtest/basic/rt66dna/1bna.pdb

regtest/basic/rt66dna/COLVAR.reference

regtest/basic/rt66dna/Makefile

regtest/basic/rt66dna/config

regtest/basic/rt66dna/plumed.dat

src/adjmat/AdjacencyMatrixBase.cpp

src/analysis/Average.cpp

src/analysis/EuclideanDissimilarityMatrix.cpp

src/analysis/Histogram.cpp

src/bias/MetaD.cpp

src/bias/PBMetaD.cpp

src/colvar/DRMSD.cpp

src/colvar/MultiRMSD.cpp

src/colvar/RMSD.cpp

src/dimred/PCA.cpp

src/dimred/PCA.h