mailcap: use open, lynx

1) I prefer opening in the background, which open -g does.
2) Turns out pandoc -> markdown ain't so hot table layouts in crap HTML mail,
   nor long links inside of them. Back to lynx. Sigh
mutt: kill the sidebar, ordering of vmailboxes

1) use 'x' (vfolder-list) instead of sidebar. It's just noise.
2) better vfolder order