Release 1.4.0

Stuff that needs sorting out, before this can be pulled:

- [x] #2096 (timeslider is broken in develop)
- [ ] <del>-> maybe #2040 / #2070</del>
- [x] #2062 (fixes #1835)
- [x] #2052 
- [x] #2068  
- [x] #2089 (changeset library fix)
- [x] #2092 (server message handler fix)
- [ ] #2097 (Connection timeout too short on poor connections)

Changelog short version is here: https://gist.github.com/marcelklehr/8586848