Revert "installed Zero, One, and MinusOne for IsHomalgLibSingularRingRep"

This reverts commit b2db570541088fe7e2f4644a8313c9baa994c7e3.

(needs libsing 0.4: thanks Max N. & Max H. & Frank & Hans)
remove homalgIOMode( "D" ) and SetAssertionLevel( 6 ) from ReducedBasisOfModule.g
renamed CancelGcd -> XCancelGcd
renamed RingMacrosForGAPWithLibSing -> RingMacrosForGAPWithSingularForHomalg
renamed HomalgFieldOfRationalsInExternalLibSingular -> HomalgFieldOfRationalsInExternalSingularForHomalg
move around some code for cleanup
renamed CommonHomalgTableForLibSingular* -> CommonHomalgTableForLibSing*
moved SingularForHomalg.g? -> LibSingular.g?
renamed IsHomalgLibSingularRingRep -> IsHomalgLibSingRingRep

and TheTypeHomalgLibSingularRing -> TheTypeHomalgLibSingRing
typo
clean up comments
renamed LibSingular -> LibSing in Labels
renamed HomalgFieldOfRationalsInLibSingular -> HomalgFieldOfRationalsInLibSing

+ renamed HomalgRingOfIntegersInLibSingular -> HomalgRingOfIntegersInLibSing
fixed header comments