#1165 CIF/BDD: Add 'repeat' variable orderer.

• Best to review per commit.
• End-user visible changes:
  • The data-based synthesis tool's advanced variable ordering option has a new variable orderer, the repeat orderer, that allows to repeatedly apply a given orderer a number of times.
  • Small fix in the data-based synthesis tool's advanced variable ordering documentation, for the reverse orderer.
• Other changes:
  • Fixed some comments of the ChoiceVarOrderer.

Closes #1165 (closed)