improve relation member handling / consistency map, tags window and relation editor

[dieterdreist]

"Previously", when you opened a relation editor and then removed a way from the relation by removing it in the tags window JOSM used to create a conflict if you didn't remove the way from the relationeditor version as well (because the way was still in the copy of the relation that is in the relation editor window).

Currently the behaviour seems to be changed like this:
Delete the way from relation from the tags window, in the relation editor the way is still included, on the screen (mappaint style) the way seems still to be in the relation, in the tags window the way is not in the relation anymore.
Hit "OK" and close the relation editor (i.e. confirm the relation as it is in the relation editor).
Now the mappaint updates and if you open the relation again in the editor, the way is not there anymore (i.e. you hit ok in the relation editor and directly again open the same relation and it is different than it was).

What it should do:
when you remove an object from a relation via the tags window, it should remove them silently from all open relation editors of this relation (there is already a confirmation dialogue for the removal of the item from the relation when you go via tags window).
If you hit "OK" on the relation editor, it must put the relation to the state that is displayed in the editor.

---

to reproduce

1. draw a rectangle
2. add it to a multipolygon relation (ctrl+b)
3. split the outer way in 2 ways
4. select one
5. open the relation editor for the relation
6. remove the object via tags window from the relation: it still is in the relation editor (but disappears if you close the editor via "ok").

URL:https://josm.openstreetmap.de/svn/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2018-03-19 22:00:20 +0100 (Mon, 19 Mar 2018)
Build-Date:2018-03-19 21:03:48
Revision:13548
Redirecting:to URL 'https://josm.openstreetmap.de/svn/trunk':
Relative:URL: ^/trunk

Identification: JOSM/1.5 (13548 en) Mac OS X 10.13.3
OS Build number: Mac OS X 10.13.3 (17D102)
Memory Usage: 854 MB / 1820 MB (372 MB allocated, but free)
Java version: 1.8.0_144-b01, Oracle Corporation, Java HotSpot(TM) 64-Bit Server VM
Screen: Display 188875522 1920x1080, Display 458628992 1920x1080
Maximum Screen Size: 1920x1080
VM arguments: [-Dsun.java2d.opengl=true]
Dataset consistency test: No problems found

Plugins:
+ ColorPlugin (1511895663)
+ Create_grid_of_ways (33856)
+ ImportImagePlugin (33563)
+ PicLayer (34021)
+ ShapeTools (1230)
+ apache-commons (33668)
+ buildings_tools (34040)
+ editgpx (33782)
+ ejml (32680)
+ fieldpapers (v0.4.3)
+ geochat (33982)
+ geojson (73)
+ geotools (33958)
+ imagery_offset_db (33774)
+ jts (32699)
+ log4j (32699)
+ mbtiles (a3e491d)
+ measurement (33760)
+ o5m (33566)
+ osmarender (33916)
+ pbf (33568)
+ photo_geotagging (33967)
+ reltoolbox (34087)
+ reverter (34036)
+ undelete (33980)
+ utilsplugin2 (33991)

Last errors/warnings:
- W: No configuration settings found.  Using hardcoded default values for all pools.
- W: Cannot start IPv4 remotecontrol https server on port 8112: Keystore was tampered with, or password was incorrect
- W: Cannot start IPv6 remotecontrol https server on port 8112: Keystore was tampered with, or password was incorrect

[skyper]

Ticket #20561 has been marked as a duplicate of this ticket.

[skyper]

See #5686.

[skyper]

As the relation editor is independent, I'd rather like to have the update button been active and displaying the correct (old) node count.