Feature: Local Multiplayer Support

[ianclawson]

This PR (in a series of PRs for Local Multiplayer Support) conforms to the updated EmulatorBridging protocol to allow for local multiplayer support, and implements sending per-player inputs to the emulator core.

Not opened in any PR is protocol conformance in the GBC, GBA, and melonDS cores. While local multiplayer support does not exist on those cores, they will still need to adopt the protocol, and may simply ignore the new incoming playerIndex var.

Other PRs:

• Delta: https://github.com/rileytestut/Delta/pull/128
• DeltaCore: https://github.com/rileytestut/DeltaCore/pull/32
• NES: https://github.com/rileytestut/NESDeltaCore/pull/2
• SNES: https://github.com/rileytestut/SNESDeltaCore/pull/2
• N64: https://github.com/rileytestut/N64DeltaCore/pull/5
• GEN: https://github.com/rileytestut/GPGXDeltaCore/pull/1

Relevant Trello Cards:

• https://trello.com/c/VtDLcykr/71-feature-nes-local-multiplayer
• https://trello.com/c/pwA1ts98/70-feature-snes-local-multiplayer
• https://trello.com/c/Mu9dQ1aZ/72-feature-n64-local-multiplayer