TLE, shortcuts, UI details

#15, #39: Added TLE handling. And the tests run sequentially. Time limit is hardcoded on 3s, but it will be editable ASAP. Also the "Abort tests" button changed to "Abort test", so new button should be added for aborting all tests.
#26: Added many keyboard shortcuts:
ctrl+n -> new problem
ctrl+b -> new contest
ctrl+t -> new testcase
ctrl+r -> run tests
ctrl+a -> abort tests
ctrl+enter in testcase dialog -> save changes
escape in all windows -> close
enter in new problem and new contest dialogs -> intuitive action
TODO: all shortcuts should be listed somewhere
#40: The result of parsing task/contest is always shown in the dialog (parsing ok/parsing failed).