Make terminal colors more consistent with UI

* swap IncSearch gui fg/bg to match original scheme
* remove some bg color settings (or change to NONE) so they don't have
  to be fixed later
* fix terminal IncSearch to match gui more closely
* introduce terminal MatchParen
* use dark green instead of grey for terminal Search bg
* terminal Todo should be a very light grey, not green
* Underlined should be underlined
* Use color 231 (#ffffff) for WarningMsg instead of the user's color15
  which is more likely to be themed by the terminal
* WildMenu should be underlined
* s/gui/cterm/ for terminal Error settings, and match the gui theme
  better

Signed-off-by: Jani Nurminen <slinky@iki.fi>