Discord RPC cleanup

- Loading Discord RPC is now handled by `load/rpc.lua`
- Removed `presence` global, call `DiscordRPC:update()` directly with what needs updating
- Game doesn't crash anymore if the Discord RPC fails to load
- Added RPC variables in the gamemode superclass to let each gamemode handle its special case

main.lua

@@ -1,46 +1,7 @@
 function love.load()
-    discordRPC = require("libs.discordRPC")
-    discordRPC.appId = "599778517789573120"
-
-    function discordRPC.ready(userId, username, discriminator, avatar)
-        print(string.format("Discord: ready (%s, %s, %s, %s)", userId, username, discriminator, avatar))
-    end
-
-    function discordRPC.disconnected(errorCode, message)
-        print(string.format("Discord: disconnected (%d: %s)", errorCode, message))
-    end
-
-    function discordRPC.errored(errorCode, message)
-        print(string.format("Discord: error (%d: %s)", errorCode, message))
-    end
-
-    function discordRPC.joinGame(joinSecret)
-        print(string.format("Discord: join (%s)", joinSecret))
-    end
-
-    function discordRPC.spectateGame(spectateSecret)
-        print(string.format("Discord: spectate (%s)", spectateSecret))
-    end
-
-    function discordRPC.joinRequest(userId, username, discriminator, avatar)
-        print(string.format("Discord: join request (%s, %s, %s, %s)", userId, username, discriminator, avatar))
-        discordRPC.respond(userId, "yes")
-    end
-
-	discordRPC.initialize(discordRPC.appId, true)
-	local now = os.time(os.date("*t"))
-	presence = {
-			startTimestamp = now,
-			details = "Loading game...",
-			state = "",
-			largeImageKey = "icon2",
-			largeImageText = "Original game by Joe Zeng",
-			smallImageKey = "",
-			smallImageText = ""
-	}
-
 	math.randomseed(os.time())
 	highscores = {}
+	require "load.rpc"
 	require "load.graphics"
 	require "load.fonts"
 	require "load.sounds"