[LyX/master] Updates for Russian, by Yuriy

[Juergen Spitzmueller]

commit 2bfb60656258386771a3d5bc15e89954866aa97d
Author: Juergen Spitzmueller <spitz at lyx.org>
Date:   Sat Jun 13 10:24:40 2020 +0200

    Updates for Russian, by Yuriy

 lib/doc/ru/Intro.lyx     |  140 +++---
 lib/doc/ru/Tutorial.lyx  |   33 +-
 lib/doc/ru/UserGuide.lyx | 1475 ++++++++++++++++++++++++++++------------------
 po/ru.po                 |  105 ++--
 4 files changed, 1026 insertions(+), 727 deletions(-)