Added return_fig boolean parameter to create_full_tear_sheet() and create_simple_tear_sheet()

[nikoulis]

Modified create_full_tear_sheet() and create_simple_tear_sheet() to optionally return matplotlib figures based on the return_fig boolean parameter, in analogy to other tear sheet functions, such as create_returns_tear_sheet(), create_position_tear_sheet() etc. Now these two tear sheet functions can be used outside of IPython (%matplotlib inline) environments to capture these tear sheets and display them, convert them to pdf files etc.

If return_fig==True, create_full_tear_sheet() now returns the following dictionary containing all the matplotlib figures that were created internally:

{
'returns': fig_returns,
'interesting_times': fig_interesting_times,
'position': fig_position,
'txn': fig_txn,
'round_trip': fig_round_trip,
'capacity': fig_capacity,
'perf_attrib': fig_perf_attrib
}

And if return_fig==True, create_simple_tear_sheet() returns the matplotlib figure already created internally.

[reisenmachtfreude]

Thanks for your pr. I need this functionality as well.

Since I just want to programmatically store pyfolio results for later analysis I can go this way
jupyter nbconvert --to pdf backtrader_backtest_pyfolio.ipynb