Direct on-terminal plot as option for headless situations

[sadielbartholomew]

On writing up #172 I had the thought that, to provide an immediate plot view in headless situations, or otherwise as a possibly useful 'quick look' feature, there are libraries that enable in-terminal primitive plots. It is firm 'bells and whistles' territory, but it is not too much code to add as a dependency to the 'climate-aware-task-scheduler[plots]' libraries some lightweight library like plotext which I've used for a brief demo below, to allow such a view.

Example

I had a quick play around and got this which I appended to the plotplan in the plotting module, to compare to the main matplotlib plot:

    import plotext as textplt
    textplt.date_form('d/m/Y H:M:S')

    def convert_dt_to_mins(dt):
        return textplt.datetimes_to_string(dt)

    conv_ci_times = convert_dt_to_mins(times)
    textplt.plot(conv_ci_times, values, fillx=True)
    textplt.plot(convert_dt_to_mins(now_times), now_values, fillx=True)
    textplt.plot(convert_dt_to_mins(opt_times), opt_values, fillx=True)

    textplt.xlim(min(conv_ci_times), max(conv_ci_times))
    textplt.ylim(0.0, max(values))

    textplt.show()

which produces:

where the reference full matplotlib plot (going from my PR branch #171 which will update the plotting) that also emerges is:

It's not perfect but for a quick-look it's decent enough...