added new combinatorial functions for tableaux and crystals

[anneschilling]

I added a two new functions
promotion and promotion_inverse
for rectangular tableaux.

I also added a reflection operator
for the crystal library.

CC: @sagetrac-sage-combinat

Component: combinatorics

Keywords: promotion, reflection

Issue created by migration from https://trac.sagemath.org/ticket/3417

[sagetrac-mabshoff]

comment:1

Hi Anne,

trac is a little tricky when pressing the submit button, so you did create a dupe. Don't worry about that, everybody did at some point.

This is a dupe of #3418.