Convert list of receipts to map<userId, timestamp>

When you run the docker-image while being offline this step avoids nheko to be build.

fixes #131

When a custom filter is inserted into nheko.conf or there was no filter
defined yet the default filter gets automatically uploaded.
After a successful upload the server-side generated filter-id is used.

This is done async as it is just an enhancement and it is not required
to upload the filter before the first request.

[ci skip]

fixes #199

[ci skip]

I had a look at sync.cpp and checked which parts of the sync response
are currently handled and which not. As I think it is unnecessary to let the 
unhandled data be transmitted without being handled I added these filters.

In the same term I increased the timeout server-side to 30s as Riot
defaults to this value as well. Especially now when a lots of presence-updates 
are not send anymore this value is more relevant.

It is now also possible to use a filter that is defined in`client/sync_filter`.
Advanced users might want to set an own filter here.

[ci skip]

fixes #197

fixes #132 

[ci skip]

fixes #168

The first distribution to have nheko in it's official repositories! 

    Right now nheko is only in the `testing` repository, but this will
    be moved to `community` after a while (after which it's available
    for installation out of the box).

[ci skip]

[ci skip]

fixes #175

fixes #2