Add a "default files folder" field

[DBinaghi]

Hello.
I was importing some files from the dropbox plugin's files folder, and realized that it would be helpful to have an option to define a default files folder during the setting up of the import process, so that I could just use the filenames instead of adding the full path for each one of them.
Maybe a simple "default files folder" field in the config page? Or, even better, since many could be using it with the dropbox plugin, check whether the plugin is active and offer a change to select that folder, or instead add a custom one.
Hope this helps.