Instead of using 2 specific IDs, a generic path to the value in the XML-file has to be given now.
This enables the plugin to also be used for other XML use cases apart from specific PDU-case.

Further testing required. Remove test code afterwards

Missing:
-Certificate validation and so on required?
-just send request.xml? or use GET or something?
-undefined symbol error when trying to load plugin

2 Bugfixes:
-correct initialization of PDUSensors with new()
-cooldown value for XML-file refresh is now correctly converted from MS to NS

Remaining TODOs:
network logic to obtain XML-file
use appropriate lock when sensor accesses PDUUnit
make reading XML more generic?
Test it!

Every sensor stores its full MQTT-topic now

Add possiblity to specifiy plugins in the global.conf
Rename plugins to libdcdbplugin_pluginName.so
Add version number to plugin-names

Remove readme.txt from perfevent