Add Styler.applyformat to set values instead of styles
I have a DataFrame that has multiple pairs of columns that are are title and URL. I would like to be able to render this table by converting the title to an anchor: `<a href=URL>title</a>`. 

Styler.format doesn't support this because the function only provides one value for a column and the format spec string doesn't support URL links.

Here's what I'd like to be able to do:
```
def to_href(title, url):
    return pd.Series([f"<a href={url[i]}>{title[i]}</a>" for i in range(len(title))])

ewm = client.executeSparql(query) # a DataFrame from a SPARQL result set
ewm.columns = ['Capability', 'Capability URL', 'Capability Status', 'Plan Item', 'Plan Item URL', 'Plan Item Status', 'Risk', 'Work Item', 'Work Item URL', 'Work Item Status']
ewmStyler = ewm.style 
ewmStyler.applyformat(to_href, axis=0, url=ewm['Capability URL'], subset='Capability')                
ewmStyler.hide_columns(['Capability URL','Plan Item URL', 'Work Item URL'])
HTML(ewmStyler.render())
```
That is, applyformat works just like apply, but set the values, not the style.

