Ports Modular Computers from Baystation

This is just the initial parts. Additional work will probably be necessary.

code/modules/modular_computers/file_system/data.dm

@@ -0,0 +1,17 @@
+// /data/ files store data in string format.
+// They don't contain other logic for now.
+/datum/computer_file/data
+	var/stored_data = "" 			// Stored data in string format.
+	filetype = "DAT"
+
+/datum/computer_file/data/clone()
+	var/datum/computer_file/data/temp = ..()
+	temp.stored_data = stored_data
+	return temp
+
+// Calculates file size from amount of characters in saved string
+/datum/computer_file/data/proc/calculate_size(var/block_size = 250)
+	size = max(1, round(length(stored_data) / block_size))
+
+/datum/computer_file/data/logfile
+	filetype = "LOG"