Bugs with many relation and refresh

[josee666]

bugs:
1- new relation add to the project not refresh in GUI
2- The relation doesn’t work the first time when you enter a project that had relation set, you have to open and close the option.
3- the relation don’t refresh when you open another project (change project)
4- select row with CTRL or SHIFT doesn't work when you are in table that have relation set

See PS and detail here: https://drive.google.com/open?id=1zelDqY1qTX6AbkewZnvVxFjscVl52d588WrknuYNc6M

Sample geopackage: https://drive.google.com/open?id=1PSDXe6gIo1cPR0Ly50_dqH8aLTJG6CNx

Thank a lot
PS: Great job, nice package!!

[slarosa]

addressed on bbcf276 (only 4 is not solved yet)

[meyerlor]

any chance 4) will also get solved anytime? :)