Allow enviroment variables in launcher commands

Allow the "Command:" field in the "Edit Launcher" dialog window to support environment variables for commands.\

For example, instead of
"/home/username/rest-of-path/application-name"
it would also allow
"$HOME/rest-of-path/application-name"

This would cover all of the following which use this "Edit Launcher" dialog
-Menu (For example Whisker Menu)
-Docklike Taskbar launchers
-Panel launchers
-Desktop icons

EDIT:
This would also apply to "Keyboard - Application Shortcuts" tab, where commands can also be launched.

Thank You

changed the description

Yes, maybe it could be made easier. In the meantime, the classic way to do it (valid for many command fields here and there) is to use a shell:

sh -c '$HOME/rest-of-path/application-name'

added 2. Enhancement 5. Launcher labels

changed the description

mentioned in issue xfce4-settings#590 (closed)

changed the description