Save picture of the day (potd)
This MR enables saving wallpaper image (currently potd) from lnf qml plugin. The image is saved into <QStandardPaths::PicturesLocation>/Saved Wallpapers.
With this change in place, a wallpaper plugin can optionally express its intent on saving the current picture (qml property supportSaving). If it supports saving, it will provide the local image uri (qml property imageSourceUrl) and optionally title (qml property imageTitle). Any lockscreen UI plugin wishing to enable this feature can query for supportSaving and call saveWallpaper() of the wallpaperItem object.
Edited by Nate Graham