Simplify: remove `dired-{next,previous}-file', which are buggy anyway
for filenames which wrap over more than one line.
Only bind keys to commands from the "sorter" library if it actually gets loaded.
Bookmarks update.
Only bind keys to commands from the "dired-rename-commands" library if it actually gets loaded.
Use the macro `require-soft' instead of calling `require' with extra arguments.