adds gating stuff, writes all thresholds simultaneously, updates readme with example

db/channels.db

@@ -48,6 +48,15 @@ record(longout, "$(INSTR)$(NAME):C$(CHANNEL)")
  field(FLNK, "$(INSTR)$(NAME):T$(CHANNEL)")
 }
 
+record(ao,"$(INSTR)$(NAME):THRESH$(CHANNEL)")
+{
+ field(DESC, "Sets minimum rate for counting to proceed")
+ field(OMSL, "supervisory")
+ field(OROC, "0")
+ field(OUT, "@$(PROTO) setMinRate($(INSTR)$(NAME):, $(CHANNEL)) $(ASYN_PORT)")
+ field(DTYP, "stream")
+}
+
 ################################################################################
 # Read all monitors values