Remove d.sh

d is basically a terrible version of the experimental version of f,
super-f.
Update todo.
Change 'ls' to 'ls -F' in 'fdr'.

This shows file symbols.
Continue generic work on 'f'.

More variables are local. There's some new argument handling. Screen
clearing is optional. Some file types have been removed. Shell detection
now works correctly. Directory selection is now more robust.
Merge branch 'master' into super-f