NTNet P2P Transfer client

- Adds simple NTNet P2P transfer client, that allows users to send files via NTNet.
- This client can act either as actual client (downloading files), or as a server, providing one file at time.
- This may (not guaranteed) be expanded in future, to allow sharing of multiple files at once, possibly even having some sort of dedicated server architecture
- Transfer speed is calculated as lower value of connection speed of both devices (weakest link in the chain)
- Server may be protected using rudimentary password that, if set, must be entered to download the file.

code/modules/modular_computers/NTNet/NTNet.dm

@@ -8,7 +8,7 @@ var/global/datum/ntnet/ntnet_global = new()
 	var/list/available_station_software = list()
 	var/list/available_antag_software = list()
 	var/list/chat_channels = list()
-
+	var/list/fileservers = list()
 	// Amount of logs the system tries to keep in memory. Keep below 999 to prevent byond from acting weirdly.
 	// High values make displaying logs much laggier.
 	var/setting_maxlogcount = 100