chore: initial import from KNEL/PFVCluster@041d311 [#769]

Split per O&M lane work order. Full history: KNEL/PFVCluster.
shellcheck debt fixed in librenms-agent (quoting, arithmetic, backticks);
fixes upstream ntp-server.sh bug: input_wakeups reported PACKETSENDFAILURES
instead of INPUTWAKEUPS. mysql.sh (PHP-in-.sh) exempt per house rule.

https://projects.knownelement.com/issues/769#note-4152

librenms-agent/agent/dpkg.sh

@@ -0,0 +1,22 @@
+#!/bin/bash
+# Cache the file for 30 minutes
+# If you want to override this, put the command in cron.
+# We cache because it is a 1sec delay, which is painful for the poller
+if [ -x /usr/bin/dpkg-query ]; then
+  DATE=$(date +%s)
+  FILE=/var/cache/librenms/agent-local-dpkg
+  
+  [ -d /var/cache/librenms ] || mkdir -p /var/cache/librenms
+  
+  if [ ! -e "$FILE" ]; then
+    dpkg-query -W --showformat='${Status} ${Package} ${Version} ${Architecture} ${Installed-Size}\n'|grep " installed "|cut -d\  -f4- > "$FILE"
+  fi
+  FILEMTIME=$(stat -c %Y "$FILE")
+  FILEAGE=$((DATE - FILEMTIME))
+  if [ "$FILEAGE" -gt 1800 ]; then
+    dpkg-query -W --showformat='${Status} ${Package} ${Version} ${Architecture} ${Installed-Size}\n'|grep " installed "|cut -d\  -f4- > "$FILE"
+  fi
+  echo "<<<dpkg>>>"
+  cat "$FILE"
+fi
+