preferences: add per account options to AutoAnswer and WaterMark

AudioFilter/ffmpeg/rules.mak

AutoAnswer/BotChatHandler.cpp

AutoAnswer/BotChatHandler.h

AutoAnswer/BotPeerChatSubscriber.cpp

AutoAnswer/BotPeerChatSubscriber.h

AutoAnswer/CMakeLists.txt

AutoAnswer/PluginPreferenceHandler.cpp

AutoAnswer/PluginPreferenceHandler.h

AutoAnswer/build.sh

AutoAnswer/data/accountpreferences.json

AutoAnswer/data/preferences.json

AutoAnswer/main.cpp

AutoAnswer/manifest.json

AutoAnswer/package.json

GreenScreen/ffmpeg/rules.mak

WaterMark/CMakeLists.txt

WaterMark/PluginPreferenceHandler.cpp

WaterMark/PluginPreferenceHandler.h

WaterMark/WatermarkMediaHandler.cpp

WaterMark/WatermarkMediaHandler.h