Add Gravity Generator, place on tether, update events

code/modules/events/gravity_vr.dm

@@ -0,0 +1,38 @@
+/datum/event/gravity
+	announceWhen = 5
+	var/list/zLevels
+	var/list/generators = list()
+
+/datum/event/gravity/setup()
+	endWhen = rand(5 MINUTES, 20 MINUTES)
+	// Setup which levels we will disrupt gravit on.
+	zLevels = using_map.station_levels.Copy()
+	for(var/datum/planet/P in SSplanets.planets)
+		zLevels -= P.expected_z_levels
+
+/datum/event/gravity/announce()
+	command_announcement.Announce("Feedback surge detected in mass-distributions systems. Artificial gravity has been disabled. Please wait for the system to reinitialize, or contact your engineering department.", "Gravity Failure")
+
+/datum/event/gravity/start()
+	gravity_is_on = 0
+
+	for(var/obj/machinery/gravity_generator/main/GG in machines)
+		if((GG.z in zLevels) && GG.on)
+			generators += GG
+			GG.breaker = FALSE
+			GG.set_power()
+			GG.charge_count = 10
+
+/datum/event/gravity/end()
+	gravity_is_on = 1
+
+	var/did_anything = FALSE
+	for(var/obj/machinery/gravity_generator/main/GG in generators)
+		if(!GG.on)
+			GG.breaker = TRUE
+			GG.set_power()
+			GG.charge_count = 90
+			did_anything = TRUE
+
+	if(did_anything)
+		command_announcement.Announce("Gravity generators are again functioning within normal parameters. Sorry for any inconvenience.", "Gravity Restored")