Adds support for 4 channel boxes and overview in Readme

db/counterbox_common.db

@@ -229,26 +229,6 @@ record(longin, "$(P):$(NAME):M4")
  field(DESC, "Counterbox CH4")
 }
 
-record(longin, "$(P):$(NAME):M5")
-{
- field(DESC, "Counterbox CH5")
-}
-
-record(longin, "$(P):$(NAME):M6")
-{
- field(DESC, "Counterbox CH6")
-}
-
-record(longin, "$(P):$(NAME):M7")
-{
- field(DESC, "Counterbox CH7")
-}
-
-record(longin, "$(P):$(NAME):M8")
-{
- field(DESC, "Counterbox CH8")
-}
-
 # Not yet sure whether we want to support this
 # record(longin, "$(P):$(NAME):R1")
 # {