GUI is disabled while connecting

Steps to reproduce:

1. while connecting to a DB which routes into a VPN

2. and this VPN doesn't return tcp/ip "destination unreacheable" error

3. or a firewall just drops the packets instead of replying "host not found"

4. the user waits for the connection to be established;

5. during this period the UI is completely irresponsible and I'm sitting and waiting for the error

6. finally a popup shows up saying "SQL Error (0): Login timeout expired"

Expected behaviour:

1. me being able to set the "Login timeout" to 5 seconds;

2. or (better) the UI stay clickable during the connection time; after the connect I will see the new DB in the tree; Heidi might "simulate" a click on the connection established if that's first ever connection; but if that's a second or next connection - nothing else should change; so when the connection fails I should see the popup and details in the log; during the timeout I should be able to execute my queries on the other connected databases;

Thanks for looking into that!