Add kill dependent and group dependent features

[roulaoregan-spi]

Summarize your change.
As per users' request, migrating a job grouping feature from the old cue.
Kill dependent will suggest killing dependent job every time a job with dependencies gets killed. Group dependents adds a checkbox to cuetopia to allow grouping dependent jobs in the JobMonitor treeView.

[akim-ruslanov]

Python unit test was failing due to the fact that self.stub.GetWhatDependsOnThis was returning a mock within self.stub.GetWhatDependsOnThis. Since the job in the unit test should have no dependency, I suggest the following:

    @mock.patch('cuegui.Utils.questionBoxYesNo', return_value=True)
    def test_kill(self, yesNoMock):
        job = opencue.wrappers.job.Job(opencue.compiled_proto.job_pb2.Job(name='job-name'))
        job.kill = mock.Mock()
        job.getWhatDependsOnThis = mock.Mock()
        job.getWhatDependsOnThis.return_value = []

        self.job_actions.kill(rpcObjects=[job])

        job.kill.assert_called()

[roulaoregan-spi]

@akim-ruslanov - thank you for looking into the unittest failure and for your suggestion! I'll apply the fix to the branch.