Refactors alerts and flow statuses in builtin and plugins

Implements #3811
Implements #3812

Refactors builtin alerts

Refactors builtin flow statuses

scripts/lua/modules/alert_definitions/alert_nfq_flushed.lua

@@ -0,0 +1,22 @@
+--
+-- (C) 2019-20 - ntop.org
+--
+
+local alert_keys = require "alert_keys"
+
+local function nfwFlushedFormatter(ifid, alert, info)
+  return(i18n("alert_messages.nfq_flushed", {
+    name = info.ifname, pct = info.pct,
+    tot = info.tot, dropped = info.dropped,
+    url = ntop.getHttpPrefix().."/lua/if_stats.lua?ifid=" .. ifid,
+  }))
+end
+
+-- #######################################################
+
+return {
+  alert_key = alert_keys.ntopng.alert_nfq_flushed,
+  i18n_title = "alerts_dashboard.nfq_flushed",
+  i18n_description = nfwFlushedFormatter,
+  icon = "fas fa-angle-double-down",
+}