On-Screen controller overlay

[nilp0inter]

Is your feature request related to a problem? Please describe.
Some game consoles like Intellivision or ColecoVision use per game overlay sheets that can be inserted into the game controller so the user can understand more easily the function of each button during the game.

This feature is not replicated in MiSTer unless you have the original overlay, controller and an adapter to connect it to the system.

Describe the solution you'd like
When playing a game which was mean to be used with an overlay, the appropriate one should be displayed in a section of WebMenu. This way it can be used as a cheatsheet or even as a remote controller (when #23 is implemented).

Additional context

• This feature was requested by @famiclone6502 via Discord.
• Some (but not all) original controller overlays has been scanned and are available via archive.org. Others can be found via regular google image search.
• @famiclone6502 pointed out that we have to be sure to have a way that two people can pull up either player 1 or player 2’s numberpad

[famiclone6502]

Thank you for considering my idea. I'll try to describe the ideal end user experience as best possible.

Two mobile phones join a user's wireless network. Player 1's phone navigates to the web interface and is able to choose Player 1's number pad, Player 2's phone also connects and is able to choose Player 2's number pad. They launch Fortune Builder for Coleco (or Utopia for Intellivision), the appropriate custom overlay for the game they launched displays on their phone screens. The users are able to independently control their respective number pads from their phones. If they load a game that does not have a custom overlay, they can either use the default number pad or choose a specific number pad style they prefer (i.e. the white Coleco Adam controller, or a later model Intellivision controller).

[famiclone6502]

The Coleco has two distinct styles of overlays, ones for the default controller and another for the "Super Action" controller. If the overlays are loaded as an image, the locations of the buttons will be different and need to be distinguished between each other.

A Coleco game can also have both a regular overlay and a "Super Action" overlay (i.e. Spy Hunter). So, the user may need to choose one when the game loads.