Added function to collect dynamic results as dict or csv

This merge request includes a single additional function that allows user to turn dynamic fitting results into a dict of dict or save into csv.

Another change is that the dynres output of dynmrs.fit() now also includes the variable mapping object as this is used by the results collection function.

To collect results, user just does something like:

dynres = dyn.fit()
res    = collect_dyn_results(dynres,to_file='myresults')

And then if in a notebook:

df = pd.DataFrame(res['conc'])
df