[Feature Request] GameFiles know what the proper IWAD is

[kenbot]

Almost all GameFiles only work with one game/IWAD and don't make any sense, or even work at all with any others. Maybe there's a handful of gameplay mods that work across Doom/Doom2? Or if they're full of textures and MIDI files? It's pretty niche though.

Currently, DoomLauncher has no opinion about this, and leaves the choice fully up to the user. This is a very poor user experience; often the correct choice is unclear and requires hunting through the TXT file or just running the game and seeing which one seems to have the content. Once you choose it, it will be saved to the profile at least, but overall it's a pain.

Suggestion:

• GameFile table gets a ProperIwad column, separate from the IWadId column (which reflects the user's choice) that contains the unique text code of the IWAD (eg "doom", "doom2", "tnt", "heretic", etc -- the ones in IWadInfo)
• Hopefully we can sharpen up detection - by examining the structure of the WAD/pk3/archive and reading the idgames TXT, hopefully that can get us most of the way
• If detection is good enough, then replace the IWad combo box in the Launch dialog with a "Change IWad..." link that is tucked away in small print at the bottom of the page
• Pressing "Change IWad..." reveals the combo box with a warning message, and another button to quickly restore it to the normal one
• When deploying, all existing user preferences can be left as is, but non-standard (ie wrong) ones will now appear with the little warning thing
• As an additional bonus, if we have rock solid info about which IWAD to use, then we could superimpose the IWAD mini-tile (the static ones in the TileImages directory) on the bottom-right corner of the thumbnail images in GameFileView, and replace the boring grey default tile with an IWAD-themed one