merged marcel's branch

...tp..mathhub.info/MitM/core/algebra/$Integer$Ring.omdoc.xz

.....mathhub.info/MitM/core/algebra/$Natural$Monoid.omdoc.xz

.....mathhub.info/MitM/core/algebra/$Rational$Field.omdoc.xz

...http..mathhub.info/MitM/core/algebra/$Real$Field.omdoc.xz

content/http..mathhub.info/MitM/core/algebra/$Rig.omdoc.xz

...hub.info/MitM/core/algebra/groups/$Group$Actions.omdoc.xz

...o/MitM/core/algebra/groups/$Permutation$Groups$N.omdoc.xz

...nfo/MitM/core/algebra/groups/$Permutation$Groups.omdoc.xz

....info/MitM/core/algebra/groups/$Stabilizer$Chain.omdoc.xz

...mathhub.info/MitM/core/algebra/groups/$Subgroups.omdoc.xz

...o/MitM/core/algebra/groups/$Symmetric$Group$Of$N.omdoc.xz

...b.info/MitM/core/algebra/groups/$Symmetric$Group.omdoc.xz

...info/MitM/core/arithmetics/$Rational$Arithmetics.omdoc.xz

...hub.info/MitM/core/arithmetics/$Rational$Numbers.omdoc.xz

...hub.info/MitM/core/arithmetics/$Real$Arithmetics.omdoc.xz

...mathhub.info/MitM/core/arithmetics/$Real$Numbers.omdoc.xz

...thhub.info/MitM/core/calculus/$Lebesgue$Integral.omdoc.xz

.../http..mathhub.info/MitM/core/geometry/$Geometry.omdoc.xz

...mathhub.info/MitM/core/geometry/$Planar$Geometry.omdoc.xz

...tp..mathhub.info/MitM/core/geometry/3$D$Geometry.omdoc.xz