Plot aggregate: fix number of bins

[sarkipo]

Hi Santiago,

-- "Plot aggregate" button is missing from the compact setup (only appears in lazy)
-- There is an error in choosing the number of bins, looks like a clash of two variables, the predefined number_of_bins and the one which stores the chosen option. As a result, when the user chooses e.g. "5" bins (which is the 3rd option), the resulting value is 3 bins. I've tried to solve this, will open a pull request