Implement Device-level Input Handling

[ImmutableOctet]

To be handled at the application level, but interpreted at the game engine level.

Input devices include:

• Mouse
• Keyboard
• Gamepads/Joysticks (multiple)

Each device type should have its own event types that relay appropriate state information, split into two categories:

• Axis/motion inputs
• Button up/down inputs

The game engine would then be able to interpret these messages/events in order to produce its own device-agnostic input events, etc.

Other features:

• Interoperate with game/engine on button mappings and device profiles.

[ImmutableOctet]

Added tag for app module. May change this to its own standalone module (rather than a submodule of app) at a later date.