Multiple loadout slots (#4530)

* Multiple loadout slots

Ported from Bay. Each character can have 3 (number can be overridden by config) loadout slots. This way, you can have different outfits for different situations without needing to have a separate character slot or edit your loadout every time.

Tested here, works as intended. The current loadout is set as slot 1, so you don't need to worry about remaking it. This also ports the to_file and from_file macros to make it work, I'm assuming they could later be used elsewhere as well.

* Log of Changing

code/modules/client/preferences.dm

@@ -50,7 +50,9 @@ datum/preferences
 	var/species_preview                 //Used for the species selection window.
 	var/list/alternate_languages = list() //Secondary language(s)
 	var/list/language_prefixes = list() //Kanguage prefix keys
-	var/list/gear						//Custom/fluff item loadout.
+	var/list/gear						//Left in for Legacy reasons, will no longer save.
+	var/list/gear_list = list()			//Custom/fluff item loadouts.
+	var/gear_slot = 1					//The current gear save slot
 	var/list/traits						//Traits which modifier characters for better or worse (mostly worse).
 	var/synth_color	= 0					//Lets normally uncolorable synth parts be colorable.
 	var/r_synth							//Used with synth_color to color synth parts that normaly can't be colored.
@@ -131,6 +133,8 @@ datum/preferences
 	b_type = RANDOM_BLOOD_TYPE
 
 	gear = list()
+	gear_list = list()
+	gear_slot = 1
 
 	if(istype(C))
 		client = C