Change systray/system tray to notification area

Submitted by sco..@..il.com

Assigned to Simon Steinbeiß @ochosi

Link to original bug (#15443)

Description

During translation i see notification area/systray/system tray i the source. Orage uses systray. Parole and power manager uses system tray Others use notification area.

So i suggest to use the same for consistency. https://docs.xfce.org/xfce/xfce4-panel/systray have systray in the url and the page says both tray icons and notification area. Seems notification area is the most used.

It might be a little confusing calling it notifcation area if it have nothing to do with notifcations (the messages on the desktop).

There is also "tray icon" in Orage and Parole could be changed to "notification icon".

Version: 1.0.2