dof changes
Changed trajectory.  Decision: we'll integrate in the com comoving referential.
Barycentre.
New barycentre.
Merge branch 'master' into Affine
Fix test (partially).
More compilation fixes.
N-body test passing.
All good.
Lint.
After eggrobin's review.
Compilation fix.
Merge pull request #138 from pleroy/Affine

Change DegreesOfFreedom to take Points instead of Vectors