Not receiving offline messages

[COM8]

Bevor you create a new issue:

- [ x ] I searched for similar issues and did not find one
- [ x ] I'm using the latest version available in the [Windows Store](https://www.microsoft.com/store/apps/9NW16X9JB5WV)

I'm submitting a...:

• Regression (a behavior that used to work and stopped working in a new release)

Current behavior:

The client wont receive any offline messages.

Expected behavior:

Receive offline messages once connection got established.

Minimal reproduction of the problem with instructions:

1. Disconnect client
2. Send message to client from an other client
3. Connect client again

Environment:

App Version(s): 
v.4.0.0 <!-- Which version of the App are you using (e.g. v.0.2.0) -->

Windows 10 Version Number: <!-- https://en.wikipedia.org/wiki/Windows_10_version_history -->
- [ ] 1809
- [ ] 1803
- [ ] 1709
- [ ] 1703
- [ x ] 1607
- [ x ] 1511
- [ x ] 1507
- [ ] Insider Build (build number: )
- [ ] Misc:

Device form factor:
- [ x ] Desktop
- [ x ] Mobile
- [ ] Xbox
- [ ] Surface Hub

Where did you got the APP from?
- [ x ] [Windows Store](https://www.microsoft.com/store/apps/9NW16X9JB5WV)
- [ ] Self-build, using a provided release source
- [ ] Self-build, repo cloned at [dd.mm.yyy] <!-- When did you clone the repo! -->
- [ ] Misc, got it from... <!-- Please tell us your source! -->

[COM8]

Sometimes it works and sometimes it doesn't. Currently not really sure when and when not...

[COM8]

Does not seem to occur anymore.

[COM8]

If you lose the connection to the internet, it takes the server a few seconds to realize it.
So he will continue sending messages that never get received/read from the TCP buffer.
Solution: Stream Management XEP-0198

[COM8]

6d2d6b6 adds a workaround for this until I was able to add Stream Management XEP-0198 support.

[Echolon]

Yes, it seems that you never receive my OMEMO messages. You should definitely check this out.

[COM8]

Yeah, this is related to #55.
sqlite-net-pcl doesn't really like it if I do a lot of transactions at once like inserting all OMEMO per keys...
This results in me having a broken SQLite connection where every further interaction with the DB fails.

[COM8]

Should be fixed now with push support.