plugins: add ChatHandler API

CMakeLists.txt

jami-qt.pro

qml.qrc

src/constant/JamiTheme.qml

src/mainview/components/CallOverlay.qml

src/mainview/components/CallViewContextMenu.qml

src/mainview/components/MediaHandlerPicker.qml

src/mainview/components/MessageWebView.qml

src/mainview/components/MessageWebViewHeader.qml

src/mainview/components/PluginHandlerItemDelegate.qml

src/mainview/components/PluginHandlerPicker.qml

src/mainview/components/RecordBox.qml

src/mainview/js/pluginhandlerpickercreation.js

src/pluginadapter.cpp

src/pluginadapter.h

src/pluginhandleritemlistmodel.cpp

src/pluginhandleritemlistmodel.h

src/pluginitemlistmodel.cpp

src/qmlregister.cpp

src/settingsview/components/PluginListPreferencesView.qml