Update de_web_plugin.cpp
Update de_web_plugin.cpp

- Add a global variable for the `DeRestPluginPrivate` instance, to enable calling `enqeueuEvent()` (amongs others) from `LightNode` (amongst others) methods, see #2475.
- Ignore _Enhanced Current Hue_ for Müller Lights, see #1209
- Add support for Müller lights special scene, see #1209

dresden-elektronik/deconz-rest-plugin,dresden-elektronik/deconz-rest-plugin,dresden-elektronik/deconz-rest-plugin,dresden-elektronik/deconz-rest-plugin,dresden-elektronik/deconz-rest-plugin