Disabled make_directory

The current use of make_directory won't ever work right for cross-platform projects. Essentially, there are two problems:

1. Different platforms put the make_directory in fundamentally different places. So on Windows it's in ProgramData, while on Linux it's in ~/.enigma. This will crash LGM if you, say, save a game in EGM format on Windows and load it in Linux.
2. Changing the default make directory doesn't even work within a single platform. At least on OS-X, changing the default make directory will cause plugins to fail to load for mysterious reasons.

(2) could be fixed, but (1) will be a pain. I propose a simpler solution: just don't expose make_directory to the user at all. It will still be platform-specific, but don't let the user see it.

If this is acceptable, let me know and I will remove the make_directory from LGM's dialog box as well (for now the user-supplied setting is simply ignored). We could also leave it there with a "<DEFAULT>" value or something.