Enabling multiple directories for images

[Git-1337]

For my use case of using multiple tools to work with the notes it is necessary to allow multiple folders for images. Currently only images in the subdirectory "i" are recognised. Another tool I use creates a subdirectory "image" when adding an image. Why not hiding all the subdirectories and using the path of the md image instead.

In addition, it would be also valuable to be able to change the default image subdirectory.

In addition, images without a note in the subdirectory "i" are added as a note, is that a wanted behaviour?