colors for crypto signatures

- valid signatures are unintrusive gray
- every other kind of signature is orange-red
not-so-bright-yellow search highlight
selector: nicer yellow
replace bright yellow with more friendly orangy-yellow
comments
various draft colors

- subject of drafts in index-mode
- draft notification message in thread-view-mode
missing message line in thread-view-mode
remove all bold flags
completion mode highlight same as search highlight
wrong contact list colors is a bug in sup
simplify widgets that use the default highlight
thread-view-mode: message patinas
add variant: inverted patinas in thread-view-mode
add screenshots