Automatically generate an explanation about each of the charts

[dicortazar]

Given that some of the charts are not self-explanatory, it is necessary to add some details in the bottom of some graphics each time a new dashboard is generated.

Thus, as similarly done in https://github.com/VizGrimoire/VizGrimoireJS/blob/master/src/SCM.js#L26, we may use that description field for this purpose. And later in the HTML specify if we want such definition or not (eg desc=false)