User able to download plots and change x and y labels

[policybot2020]

• make label editing below the images
• export images button below each image

[policybot2020]

• ISSUE: NOT DOWNLOADABLE output$downloadpic2 <- downloadHandler( filename = "cumulative_plot.png", content = function(file) { png(file) plot(impact_model()) dev.off() })

plot(impact_model()):: is not a png or is not same format as maplot()

[policybot2020]

@isomemo

UPDATE: now user can edit x and y and title of the Matplot.

AND as well as download the plot to png format.

[policybot2020]

done.