There was an error in amperometry2df(), whereby the timediff calculated
was way too low. Was possibly related to the It2charge() function
used to calculate those values. That function (in common.R) is no longer
used by amperometry2df().
Also updated amperometry2df() so it now includes the data attributes
in the return dataframe itself, as columns (compare cv2df()).
common.R: do not use the It2charge() function in the future.
Do such calculations inline instead.
Be advised: This change will break all old reports that used the cv2df() function.
Experimental information (potential limits, scanspeeds, etc.) are now added to the
return dataframe as columns instead of attributes.
With this information built-in to the dataframe, analysis is simplified using melt
and cast and other grouping functions.