clarify and update docs

docs/proto_v0.txt

@@ -139,20 +139,23 @@ router's full identity
   k: "<32 bytes public long term identity signing key>",
   n: "<optional max 32 bytes router nickname>",
   p: "<32 bytes public path encryption key>",   
-  u: next_update_needed_milliseconds_since_epoch_uint64,
+  t: time_signed_at_milliseconds_since_epoch_uint64,
   v: 0,
   x: [ Exit, Infos ],
   z: "<64 bytes signature using identity key>"
 }
 
 
+RC.t is the timestamp of when this RC was signed.
+RC is valid for a maximum of 1 hour after which it MUST be resigned with the new
+timestamp.
+
 RC.i is set to the network identifier.
 
 only routers with the same network identifier may connect to each other.
 
-"loki-test" for lokinet testnet
-"loki-stage" for lokinet staging
-"loki-main" for the "official" lokinet mainline network.
+"lokinet-test" for testnet.
+"lokinet" for the "official" lokinet mainline network.
 
 other values of RC.i indicate the router belongs to a network fork.