Allow names to be used with forceskin

Allows you to use skin names as possible values for the forceskin console variable. Example from the help command.

$help forceskin
Variable forceskin:
  flags :NETVAR ACTION CHEAT 
  -1 : Off
  0  : sonic
  1  : tails
  2  : knuckles
  3  : eggman
  4  : metalsonic
 Current value: Off

Task:

• Test with recent skin changes.