Feature Request: to show only specific figure created in `plotting.py` instead of using `plt.show` we use `fig.show`.

Nobody has claimed this yet.

Running the code below, Python will pop up the window (figure) created in `plotting.py` and also the `userfig` window I created independently in this piece of code. Usually if people want to show the `userfig` they can just run `userfig.show()`.
```
userfig,ax = plt.subplots() #I want the userfig to be only showed when I use userfig.show()

dataset = pd.read_csv('data.csv', index_col=0, parse_dates= True)
n = len(dataset)

mpf.plot(dataset, type='candle', style='yahoo')
```

This is due to in `plotting.py` it uses `plt.show` (which shows all figures created in your Python code, including outside the `plotting.py`) instead of specific figure `fig.show` to show only the figure created in `plotting.py`. The downside of using `fig.show` is that it does not have `block` argument, but i think this is not a problem, since the user can use `plt.show` independently outside the `plotting.py` if he needs the `block`. I propose this change in `plotting.py`:

**BEFORE**:

**AFTER**:

Start in plotting.py and reproduce the provided example with a separately created userfig and a candlestick plot from data.csv. Check the display behavior with the current and proposed figure-specific call; done means plotting the dataset does not also display the independently created userfig, while users can still call plt.show() separately.

Written by the indexing model from the issue text.