Rename Master to Controller

The role of the master server as the party controlling every part of the
cluster is not well reflected in its name and has caused confusion among
users on several occasions.  Rename master to controller to better
reflects its role.

plugins/research_sync/module/sync.lua

@@ -27,7 +27,7 @@ sync.events[clusterio_api.events.on_server_startup] = function(event)
 		}
 	end
 
-	-- Used when syncing completed technologies from the master
+	-- Used when syncing completed technologies from the controller
 	global.research_sync.ignore_research_finished = false
 
 	local force = game.forces["player"]
@@ -165,14 +165,14 @@ function research_sync.update_progress(data)
 	local techs = game.json_to_table(data)
 	local force = game.forces["player"]
 
-	for _, masterTech in ipairs(techs) do
-		local tech = force.technologies[masterTech.name]
-		if tech and tech.level == masterTech.level then
+	for _, controllerTech in ipairs(techs) do
+		local tech = force.technologies[controllerTech.name]
+		if tech and tech.level == controllerTech.level then
 			send_contribution(tech)
-			set_technology_progress(tech, masterTech.progress)
+			set_technology_progress(tech, controllerTech.progress)
 			global.research_sync.technologies[tech.name] = {
 				level = tech.level,
-				progress = masterTech.progress
+				progress = controllerTech.progress
 			}
 		end
 	end