Display a toast while saving files

[naoliv]

Could JOSM display some kind of message while locally saving the data?
It's specially important for cases where we are saving a lot of data: JOSM just stays frozen without any feedback if it's really saving the file or not.

JOSM:

Relative:URL: ^/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2018-09-02 22:28:43 +0200 (Sun, 02 Sep 2018)
Revision:14220
Build-Date:2018-09-03 01:32:21
URL:https://josm.openstreetmap.de/svn/trunk

Identification: JOSM/1.5 (14220 en) Linux Debian GNU/Linux testing (buster)
Memory Usage: 1092 MB / 7168 MB (891 MB allocated, but free)
Java version: 10.0.2+13-Debian-1, Oracle Corporation, OpenJDK 64-Bit Server VM
Screen: :0.0 1600x900, :0.1 1280x1024
Maximum Screen Size: 1600x1024
Java package: openjdk-10-jre:amd64-10.0.2+13-1
Java ATK Wrapper package: libatk-wrapper-java:all-0.33.3-21
VM arguments: [--add-modules=java.activation,java.se.ee, -Dawt.useSystemAAFontSettings=gasp]
Program arguments: [--language=en]
Dataset consistency test: No problems found

[simon04]

In 17628/josm:

fix #16709 - Display a notification while/after saving files

[Don-vip]

In 18135/josm:

see #16709 - fix #20755 - Display a notification while/after saving session files