Change string manipulation to C++ string class

std::string seems to be the preferred method since you don't need to alloc
more memory then you need (the Class automagically allocates the necessary
RAM) and there is no chance of buffer overflow. But since I don't have Mac
OSX, I didn't test it (it should work, since this is standard C++).

Add Mac OSX support to Launcher{Market,Email} too and changed Linux to use
"xdg-email " instead "xdg-open mailto:" since this seems the preferred method.