MBS-5637: Copy warp's script from http://codereview.musicbrainz.org/r/2464/diff/
MBS-5637: Amend and update FixLinkDuplicates script, add limit option
MBS-5637: make a long-running upgrade script to fix links slowly, over time
MBS-5637: only touch the one l_ table that actually needs to be looked at
MBS-5637: remove link_tables function
MBS-5637: fix shift on reference, no-attribute link rows
Merge branch 'mbs-5637-cleanup-script' into beta

* mbs-5637-cleanup-script:
  MBS-5637: fix shift on reference, no-attribute link rows
  MBS-5637: remove link_tables function
  MBS-5637: only touch the one l_ table that actually needs to be looked at
  MBS-5637: make a long-running upgrade script to fix links slowly, over time
  MBS-5637: Amend and update FixLinkDuplicates script, add limit option
  MBS-5637: Copy warp's script from http://codereview.musicbrainz.org/r/2464/diff/