create display::blindfold accessors
create blindfold struct
use blindfold struct in playmp controller to implement feature
implement blindfold by shroud
minimap does not draw units if blindfolded

display.show_everything() returns false if blindfolded
units now say that blind observers can't see them
try to disable reachmap info in blindfold
Merge pull request #111 from cbeck88/blindfold_ii

Blindfold ii