Improve detection of changeset hashtags

[Don-vip]

What steps will reproduce the problem?

1. See ​https://twitter.com/sp8962/status/1011921459751636992 we should not detect #59606086 as a hashtag
2. We should also make sure that #foo, results in #foo (take care of trailing commas)

What is the expected result?

What happens instead?

Please provide any additional information below. Attach a screenshot if possible.

Revision:13993
Is-Local-Build:true
Build-Date:2018-07-01 15:51:39

Identification: JOSM/1.5 (13993 SVN en) Windows 10 64-Bit
OS Build number: Windows 10 Pro 1803 (17134)
Memory Usage: 308 MB / 4088 MB (175 MB allocated, but free)
Java version: 10.0.1+10, Oracle Corporation, Java HotSpot(TM) 64-Bit Server VM
Screen: \Display0 1920x1080, \Display1 1920x1080, \Display2 1280x1024
Maximum Screen Size: 1920x1080
VM arguments: [--add-modules=java.se.ee, --add-exports=java.base/sun.security.util=ALL-UNNAMED, --add-exports=java.base/sun.security.x509=ALL-UNNAMED, --add-opens=java.prefs/java.util.prefs=ALL-UNNAMED, --add-opens=java.desktop/javax.swing.text.html=ALL-UNNAMED, --add-exports=jdk.deploy/com.sun.deploy.config=ALL-UNNAMED, --add-opens=java.desktop/javax.imageio.spi=ALL-UNNAMED, --add-exports=java.desktop/com.sun.imageio.spi=ALL-UNNAMED, --add-opens=java.base/jdk.internal.loader=ALL-UNNAMED, --add-opens=java.base/jdk.internal.ref=ALL-UNNAMED, --add-opens=java.base/java.lang=ALL-UNNAMED, --add-opens=java.base/java.nio=ALL-UNNAMED, --illegal-access=deny, -agentpath:C:\ProgramData\YourKit\2018.04.73.14641094\64\yjpagent.dll=delay=10000, -Dfile.encoding=UTF-8]

Plugins:
+ austriaaddresshelper (1525848529)
+ buildings_tools (34212)
+ continuosDownload (1529090613)
+ contourmerge (1033)
+ editgpx (34109)
+ utilsplugin2 (34286)

Map paint styles:
- https://josm.openstreetmap.de/josmfile?page=Styles/Lane_and_Road_Attributes&zip=1
- %UserProfile%\Desktop\boo.mapcss
- https://pasharm.github.io/New_basic_style_for_JOSM/New_basic_style.mapcss

Validator rules:
+ C:\SVN\josm\core\data\validator\deprecated.mapcss

Last errors/warnings:
- W: No configuration settings found.  Using hardcoded default values for all pools.

[Don-vip]

In 13994/josm:

fix #16447 - Improve detection of changeset hashtags