Forge should inform users when they are attempting to run on an unsupported JRE version

*nix:
#-------------------------
JAVAVER=`$JAVACMD -version 2>&1`
case $JAVAVER in
1.[6-9]) ;;
1.[1-5])
echo " Error: a Java 1.6 or higher JRE is required to run Forge; found [$JAVACMD -version == $JAVAVER]."
exit 1
;;
esac

*windoze
#-----------------------
????