#43 Adding subdirs for pattern selection

[treteimer]

Settings/Ambient settings/Background/File supports to be given a directory wherefrom Ambient selects one randomly on every refresh.The only missing feature of it is to support subdirectories. My backdrops are sorted into different dirs like mos/, winter/, ocean/ and so on to not keep thousands of pictures of different themes in the same directory and lose oversight.
The same function was to be used in Settings/System settings/Screenmode/any public screen/Background. This one only supports one direct file.