fixed many many ordering so that other many many lists with the same relation aren't affected
Merge branch 'ManyManyRelationOrdering' of git://github.com/dnadesign/silverstripe-gridfieldextensions

* 'ManyManyRelationOrdering' of git://github.com/dnadesign/silverstripe-gridfieldextensions:
  fixed many many ordering so that other many many lists with the same relation aren't affected