Refactor class `ParametricPlotArgs`

Class ParametricPlotArgs should be renamed class PlotArguments.

This class is used to store plotting's arguments and should be created when reading a YAML configuration file.

Examples of several YAML files containing parameters for PlotArguments:

Single mode:

simulation:
  mode: single

  outputs:
    output_folder: 'examples/basic/output'
    single_plot:
      y: 'detector.image.array'
      plot_type: 'histogram'
      plot_args:                     <--+
        bins: 200                       |
        xlabel: 'ADU'                   |-- PlotArguments
        yscale: 'log'                   | 
        title:  'image histogram'.   <--+
...

Calibration mode:

simulation:

  mode: calibration

  calibration:
    calibration_mode:     pipeline
    ...

  outputs:
    output_folder:        'examples/CTI/output'
    calibration_plot:
      champions_plot:
        plot_args:
          yscale: 'log'
      population_plot:
        columns: [2, 4]
        plot_args:                        <--+
          xscale: 'log'                      |
          yscale: 'log'                      |
          title: 'trap specie #1'            |-- PlotArguments
          xlabel: 'release time (s)'         |
          ylabel: 'density (cm$^{-3}$)'.  <--+

Parametric mode

simulation:

  mode: parametric

  parametric:
    parametric_mode: sequential
    parameters:
      - key: pipeline.photon_generation.illumination.arguments.level
        values: numpy.unique(numpy.logspace(0, 6, 100, dtype=int))

  outputs:
    output_folder:  'examples/PTC/output'
    parametric_plot:
      x:  'detector.image.mean'
      y:  'detector.image.std_deviation'
      plot_args:                            <--+
        title: 'CCD Photon Transfer Curve'     | 
        xscale: 'log'                          |
        yscale: 'log'                          |-- PlotArguments
        xlim: [1., 2.e+6]                      |
        ylim: [1., 3.e+4]                      |
        grid: true                          <--+