.screenrc: Lower-contrast hardstatus colors and show sessionname
.term_colorpalette: Tweak 'blue' and 'white' colors

* Brighten 'blue' so that it's more readable against dark
  backgrounds.
* Darken 'white' so that it's more gray than white:
  Black = Black , BrBlack = DarkGrey, White = Gray, BrWhite=White
* Brighten 'black' a wee-wee-bit.