Rename Slave to Host

The role of a slave as a host for Factorio servers is not well reflected
in its name and has caused confusion among users.  Rename slave to host
to better reflect its role as a host of Factorio servers.

packages/host/lua/clusterio_lib/api.lua

@@ -0,0 +1,67 @@
+-- Important: Keep this API in sync with modules/clusterio/api.lua
+local api = {}
+
+
+local initialized = false
+function api.init()
+	if initialized then
+		return
+	end
+	initialized = true
+
+	if remote.interfaces.clusterio_api then
+		api.events = remote.call("clusterio_api", "get_events")
+	else
+		local null_event = script.generate_event_name()
+		api.events = {
+			on_instance_updated = null_event,
+			on_server_startup = null_event,
+		}
+	end
+end
+
+local function call_api(fn, ...)
+	if remote.interfaces.clusterio_api and remote.interfaces.clusterio_api[fn] then
+		return remote.call("clusterio_api", fn, ...)
+	else
+		return nil
+	end
+end
+
+function api.get_instance_name()
+	return call_api("get_instance_name")
+end
+
+function api.get_instance_id()
+	return call_api("get_instance_id")
+end
+
+
+function api.send_json(channel, data)
+	if not remote.interfaces.clusterio_api then
+		return
+	end
+
+	-- Escape bad characters.  The question mark is used for separating the
+	-- channel name from the payload.
+	channel = channel:gsub("([\x00-\x1f?\\])", function(match)
+		return "\\x" .. string.format("%02x", match:byte())
+	end)
+
+	data = game.table_to_json(data)
+
+	-- If there's more than about 4kB of data users running with the Windows
+	-- console open will start to experience stuttering, otherwise we could
+	-- output about 1 MB of data at a time through stdout.
+	if #data < 4000 then
+		print("\f$ipc:" .. channel .. "?j" .. data)
+	else
+		local file_no = remote.call("clusterio_api", "get_file_no")
+		local file_name = "clst_" .. file_no .. ".json"
+		game.write_file(file_name, data, false, 0)
+		print("\f$ipc:" .. channel .. "?f" .. file_name)
+	end
+end
+
+
+return api