- start implementing round-trip pubsub monitoring

...ala/org/bigbluebutton/endpoint/redis/RedisPublisher.scala

bbb-common-message/build.sbt

.../org/bigbluebutton/common/messages/PubSubPingMessage.java

.../org/bigbluebutton/common/messages/PubSubPongMessage.java

...button/common/messages/StartCustomPollRequestMessage.java

...src/main/java/org/bigbluebutton/common/messages/Util.java

...ton/common/messages/payload/PubSubPingMessagePayload.java

...essages/payload/StartCustomPollRequestMessagePayload.java

...on/common/messages/StartCustomPollRequestMessageTest.java

bigbluebutton-apps/build.gradle

...ebutton/red5/monitoring/BbbAppsIsAliveMonitorService.java

...ton/red5/pubsub/redis/GenericObjectPoolConfigWrapper.java

.../org/bigbluebutton/red5/pubsub/redis/MessageReceiver.java

...va/org/bigbluebutton/red5/pubsub/redis/MessageSender.java

...on-apps/src/main/webapp/WEB-INF/bbb-red5-redis-pubsub.xml

...luebutton-apps/src/main/webapp/WEB-INF/bbb-redis-pool.xml

bigbluebutton-apps/src/main/webapp/WEB-INF/red5-web.xml