Added warning for unsupported file types

[mazunki]

• removed warning about used exception var
• added warning about incompatible filetype extensions
• commented unused variables from legacy commented code, thus removing warnings

[mazunki]

I was struggling to export an NBT file to JSON through the NBTUtil. After digging into the code I realized there was a hardcoded regex patterns to match filetypes. I added a warning for these cases. Since the tool is intended for Minecraft, I didn't add the .tplr|.twld which is used by TModLoader (a Terraria Mod Loader), but would be nice if it was there. Regardless, some verbosity changes and warnings have been amended.