Help Wanted: Add MQTT support

[OliverParoczai]

We need someone who could replace GCM with MQTT(Its already implemented in the API server, check out its repo for documentation on implementing it)

[paynemiller92]

I can take a stab. I just recently integrated MQTT with the app I work on full time.

[paynemiller92]

@Olika120 can you please list the MQTT Connection properties? e.g. Protocol, URL, Username, Password, and Port number?

[OliverParoczai]

Hey! Thanks for the reply, if you could join our Slack at https://join.slack.com/t/fosspush/shared_invite/enQtNDU3MzAzNTEwMTEzLWFhNzVjYWUxNTE5MjZkYzYzZWNjYzdmZDM4ZTc5ZGJjYjYyYTVmYmZkYzgwNTA4NmE4YzMwNjNlNjFjMzY0ZjI that would be appreciated. If not, i can get someone there who works on the API server to give you some starting points.

[VoliKoN]

In addition, gcm and play services should be removed completely from the android app.
This is critical for uploading it to fdroid.