Fixed broken unit tests.
Added test for checking that when FOLDER_AFFECTS_URL is set file names in the clipboard are unique
Also added a context manager for overriding filer settings in tests.
Read FOLDER_AFFECTS_URL from the corresponding project settings
Validate folder name uniqueness on folder renames on folder moves/copying.
Fix for #304: make 'copy files and/or folders' work when the current folder is the root folder.