Add option to generate heapdump file and improve metrics

...imports/api/annotations/server/handlers/whiteboardSend.js

.../imports/api/meetings/server/modifiers/meetingHasEnded.js

bigbluebutton-html5/imports/startup/server/index.js

bigbluebutton-html5/imports/startup/server/metrics.js

bigbluebutton-html5/private/config/settings.yml