"OK" button in the "Application Settings" dialog should be locked during external tools validation

Now, if you choose some External Tool and accept the "Application Settings" dialog before a validation task ends, the current External Tool won't be validated. The "good" solution for this problem (see the linked issue) is difficult enough, so, there is a temporary solution to avoid this problem:
1. The "OK" button of the "Application Settings" dialog should be locked during the External Tools validation tasks
2. The tool state (the path to the current External Tool) should be written to the ".ini" file when the tool's validation task ends (now it happens when you click on the "OK" button)