some details in LS paths crystals

<div id="comment:0"></div>

just a few ones, not a complete cleanup

CC:  @mantepse @tscrim

Component: **combinatorics**

Author: **Frédéric Chapoton**

Branch/Commit: **[`0cb07df`](https://github.com/sagemath/sagetrac-mirror/commit/0cb07dfcc3c067278dc1cf3f4a867e51df42d7e0)**

Reviewer: **Travis Scrimshaw**

_Issue created by migration from https://trac.sagemath.org/ticket/34531_

