Should not create dialogs at the middle of two screens + should remember the dialog position

[naoliv]

See the attached video, please.

It's a dual monitor setup (not exactly one big screen, since I can change the left and right side areas independently).

When I open some dialogs, like the turn restriction in this example, part of the dialog gets on the other monitor, making me move it every time. This is one problem: dialogs should not open at the other monitor like this.

Also, if I move the dialog to some position, I expect that I will open at this same place on the next time (I am fine if this could not get implemented).

JOSM:

URL:http://josm.openstreetmap.de/svn/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2016-11-06 20:18:38 +0100 (Sun, 06 Nov 2016)
Build-Date:2016-11-06 21:45:03
Revision:11223
Relative:URL: ^/trunk

Identification: JOSM/1.5 (11223 pt_BR) Linux Debian GNU/Linux testing (stretch)
Memory Usage: 490 MB / 10206 MB (66 MB allocated, but free)
Java version: 1.8.0_111-8u111-b14-2-b14, Oracle Corporation, OpenJDK 64-Bit Server VM
Screen: :0.0 1600x900, :0.1 1280x1024
Maximum Screen Size: 1600x1024
Java package: openjdk-8-jre:amd64-8u111-b14-2
Java ATK Wrapper package: libatk-wrapper-java:all-0.33.3-9
VM arguments: [-Dawt.useSystemAAFontSettings=on]
Dataset consistency test: No problems found

[naoliv]

If this can help, my setup is:
Left side monitor with 1280x1024
Right side monitor with 1600x900

This turn restriction dialog has 600x600 and starts at 1140 (from the total width of 2880 (1280 + 1600))

[johsin18]

Will be followed up on in #16530.