Add keras_to_mdf helper function

[Onoyiza]

Hi @pgleeson. I have created a new branch that has the script for the 'keras_to_mdf' helper function. I had not added the example yet but intend to do that today. I am currently having issues getting more information using the 'level' parameter. When I use a level above 1, I get a shape attribute error. I am using the example notebook I created to test it. I will update the branch today with an example script and make updates to the script that generates the keras_to_mdf function.

[pgleeson]

Thanks @Onoyiza. I've changed this to be a pull request to the keras_interface branch, so we can both make changes there and then merge to development when it's stable.

Feel free to add your example script here and I can try it out. The issue with the level/shape when exporting to graph is probably just something small.