Status Report: add relative timestamp to last errors/warnings

[simon04]

To get an idea when the errors/warnings occurred relative to JOSM start, let's add a relative timestamp (in seconds):

Revision:16904
Is-Local-Build:true
Build-Date:2020-08-23 10:16:40

Identification: JOSM/1.5 (16904 SVN en) Linux Arch Linux
Memory Usage: 350 MB / 3844 MB (120 MB allocated, but free)
Java version: 11.0.8+10, N/A, OpenJDK 64-Bit Server VM
Look and Feel: javax.swing.plaf.metal.MetalLookAndFeel
Screen: :0.0 3840x2160 (scaling 1.0x1.0)
Maximum Screen Size: 3840x2160
Best cursor sizes: 16x16 -> 16x16, 32x32 -> 32x32
VM arguments: [-agentlib:jdwp=transport=dt_socket,address=127.0.0.1:46605,suspend=y,server=n, -Djosm.home=<josm.pref>, -javaagent:/home/simon/.local/share/JetBrains/Toolbox/apps/IDEA-C/ch-0/202.6397.94/plugins/Groovy/lib/agent/gragent.jar, -javaagent:/home/simon/.local/share/JetBrains/Toolbox/apps/IDEA-C/ch-0/202.6397.94/plugins/java/lib/rt/debugger-agent.jar, -Dfile.encoding=UTF-8]
Program arguments: [--set=expert=true, --set=iso.dates=true, --set=debug.edt-checker.enable=true, --set=tls.add-missing-certificates=false, /tmp/b2.osm]
Dataset consistency test: No problems found

Last errors/warnings:
- 00002.973 W: sdfsdf

[simon04]

In 16905/josm:

fix #19696 - Status Report: add relative timestamp to last errors/warnings

[simon04]

In 16945/josm:

see #19696 - Fix unit tests