Minimal `DataViewerApp` part 4: Final

[kangz12345]

This closes #144.

I'm sorry for the large diffs. I will try to separate it if you feel too much.

Initial state:

After clicking "Sync":

Dataset user guide

Users have to build their dataset in the following format:

class Test(EnvExperiment):
    def prepare(self):
        self.set_dataset("name", [], broadcast=True)  # must not be in @kernel
        self.set_dataset("name.parameters", ["Param1", "Param2"], broadcast=True)
        self.set_dataset("name.units", ["Unit1", ""], broadcast=True)  # no unit for param2

    @kernel
    def run(self):
        cnt = 0  # photon count
        value1 = 1e-6  # param1 value
        value2 = 2  # param2 value
        self.append_to_dataset("name", [cnt, value1, value2])

Then in the GUI, enter the dataset name "name" in the line edit and click "Sync" button. Then the axis combo boxes will work. After selecting the axes, click "Apply" button.

"Remote" mode is not implemented yet - will be implemented later (not in this PR)!

[BECATRUE]

Could you attach a screenshot?