add manual option for install DOSbox games

when click install DOSBox add the option manual install in the screen :

yes, my game is already installed on a folder. no, i have the installation media.

could have a third option that said install manually and just launch dosbox default so the user could enter manually all necessary commands to install the game, once the game run and dosbox close it the wizard ask for the game name to scrappit and add it.