Receive messages on a non-UI thread

[HawkiesZA]

When setting a new callback, messages are received on the UI thread. This completely locks up the UI if there are lots of messages being received. This has been discussed before here: #207, but it seems that the solution was never implemented.

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[tabilzad]

LocalBroadcastManager is a lot more efficient than global broadcasting through context. With the latter if the massage payload is too big - it will throw a TransactionTooLargeException.

[HawkiesZA]

While that may be true, LocalBroadcastManager doesn't appear to have a way to address the problem of locking up the UI thread as explained above. I think this may just be a quick fix under the current situation, but actually we should be looking at a different pattern rather than BroadcastManagers, considering that LocalBroadcastManager has been deprecated as well.

[ishdemon]

Use HiveMqtt instead of paho..its better maintained.