Suggest to overwrite image files after modifications

By now, when a user edits images using Android clients it saves the resulting files as new ones by adding the `edited` suffix.
Quite often a user needs to change the file but not to create new files. After several sequential modifications, a lot of files may be stored, which is not so convenient.

I suggest adding the option to let a user choose whether to overwrite existing files or create new ones when changed.