Do not save edited photos as new files

[oleua]

Every time when I use the embedded web app to edit images and click Save button the app it saves them as <filename>_edited.jpg, which is not convenient, as I am looking for the changes in the file I have changed.

I suggest changing the behaviour of how the edited images are saved:

1. When clicking Save button the existing image file is overwritten
2. Add a new button Save as a new file which will prompt the new name for the edited file.

[joshtrichards]

Some improvement via #2835