A few more changes for Vim

Tweak the text editing settings (softtabstop, textwidth, etc).

Add some settings to turn on folding and colorcolumn.

Add the undo_ftplugin changes that my previous patch forgot.
I would do this because keys like `zR` and `zM` actually change the local `foldlevel`, so I can't trust whatever level existed locally. Only the global level represents what the user wants as their default.