Adds the option display.escape_notebook_repr_html
Adds the option `display.escape_notebook_repr_html` for controlling HTML escaping when rendering DataFrames in IPython notebooks. Unset, this argument does not change the default behaviour.  

Fixes #11062

open to these types of things, but:
- use a `display.html` name space for these types of options. (or maybe `display.notebook`, but would have to rename some of the existing options possibly)
- I think we need a more general soln.
 pls update
 closing, but if you would like to continue working on this pls reopen
