Create a new plot recipe that plots the RT prices in MWh

[rafaelamaribeiro]

The idea on this code is to make a graphic where the price for the RT is given as $/MWh and not as, for example, $/MW-5min (because on this example the RT prices are evaluated for 5 in 5 minutes). To do that, the idea is to sum all the evaluated prices for each hour and to plot it.

"""
plot_prices_RT(
market_simulator::MarketSimulator,
results::SimulationResults;
bus_names::AbstractArray=[])

Plot the simulation prices over the time period covered by the results. The bus_names
control which buses we want to include the plot. It evaluates the prices for a Real Time (RT)
example and sums the prices so that it is on $/MWh.
"""

@userplot plot_prices_RT
@recipe function f(p::plot_prices_RT; bus_names::AbstractArray=[])
    market_simulator, system_results, = p.args

    prices = evaluate_prices(market_simulator, system_results)

    values = select(prices, Not(:DateTime))
    n_prev, n_bus = size(values)

    intervals = get_time_series_params(market_simulator.system_rt).interval
    
    n_prev_hour = Int(60/intervals.value)
    n_days = Int(n_prev/n_prev_hour)
    
    names_bus = names(values)
    prices_rt = zeros(n_days,n_bus)

    i = 1
    while i < n_days
        for j in 1:(n_prev_hour):n_prev
            prices_hour = prices[prices[j,:DateTime] .<= prices.DateTime .< prices[j,:DateTime]+Hour(1), :]
            prices_hour = select(prices_hour, Not(:DateTime))
            prices_rt[i,:] = sum(Matrix(prices_hour), dims = 1)
            i = i + 1
        end
    end

    times = prices[1:n_prev_hour:n_prev, 1]
    
    dictionary = Dict()
    n_row, n_col = size(prices_rt)

    for price in 1:n_col
        if !haskey(dictionary, names_bus[price])
            dictionary[names_bus[price]] = prices_rt[:,price]
        else
            dictionary[names_bus[price]] = dictionary[names_bus[price]] + prices_rt[:,price]
        end
    end

    plot_data = DataFrame(dictionary)

    # select rows for the given bus names, default to all buses.
    if !isempty(bus_names)
        bus_names = String.(bus_names)
        @assert issubset(bus_names, names(plot_data))
        select!(plot_data, bus_names)
    end

    label --> reduce(hcat, names(plot_data))
    yguide --> "Prices (\$/MWh)"
    legend --> :outertopright
    seriestype --> :line
    xrotation --> 45

    for i in Base.axes(plot_data, 2)
        @series begin
            times, plot_data[:, i]
        end
    end
end

When it is called as plot_prices_RT(market_simulator, results; xtickfontsize=8, size=(800, 600)) it seems that it does not work because of the the extra arguments (xtickfontsize and size).
ERROR: got unsupported keyword arguments "xtickfontsize", "size"

When it is called as plot_prices_RT(market_simulator, results;) it still does not work.

For now, this graphic was made in the example file using the plot function.