[Linux] Loader does not install properly

[Treeways]

The mod loader installation for Linux should overwrite the vanilla executable.

Off the top of my head, the installation could look like this:

1. Th script detects whether a vanilla FEZ executable is in the folder, whether that is FEZ.exe with a matching signature, or a previously backed up FEZ.vanilla.exe.
2. MonoMod patches that with a bundled version of mono. ([Linux] Bundle proper Mono version with HAT patcher #21)
3. The vanilla FEZ executable is backed up.
   a. Vanilla executables get backed up as FEZ.vanilla.exe.
   b. If a previously patched (MonoModded) FEZ executable already exists, it gets renamed to FEZ.exe.bak1, FEZ.exe.bak2, etc.
4. The modded executable is renamed from MONOMODDED_FEZ.exe to FEZ.exe, overwriting the original FEZ executable.

This would prevent the need to create duplicate files in the game directory, allowing the vanilla FEZ MonoKickstart runner to launch our patched executable on any supported architecture, even from Steam.

See also: #23

[Krzyhau]

It's more often for me to see a modding environment adding another executable instead of overriding the original one. I think we should stick to that. I see no problem in duplicating a couple of files. If launching from Steam is a requirement, we could modify the launch script to ask user whether wants to launch modded version or vanilla version. This way you also would just have a single duplicate of a MonoKickstart instance.

In any case, this definitely requires a modification of installation script. I've explained it little bit more in #25