add double quote to prevent simulation fail by space in filename

Fix issue #28 
The problem is that space in project name will cause qucsconv think the string before space as the output file name. Add a double quote on output file name solve this issue.
I didn't fix the qucsdigi.dat and qucsveri.dat since I'm not sure will windows handle string variable like shell script. Also, there may have other problem in qucsdigilib which I'm not sure.