Sprinting, Stamina and Temporary Modifiers (#1030)

Introduces:
- Temporary modifiers process and datums for that
- A new stamina and sprinting mechanic. That is in need of further development! Weee!

code/controllers/Processes/modifier.dm

@@ -0,0 +1,22 @@
+/datum/controller/process/modifier/setup()
+	name = "modifiers"
+	schedule_interval = 10
+	start_delay = 8
+
+/datum/controller/process/modifier/started()
+	..()
+	if(!processing_modifiers)
+		processing_modifiers = list()
+
+/datum/controller/process/modifier/doWork()
+	for(last_object in processing_modifiers)
+		var/datum/modifier/O = last_object
+		if(isnull(O.gcDestroyed))
+			O.process()
+		else
+			catchBadType(O)
+			processing_objects -= O
+
+/datum/controller/process/modifier/statProcess()
+	..()
+	stat(null, "[processing_modifiers.len] modifiers")