User should be able to view PageElements in Jupyter

[anders-kiaer]

webviz is close to have native support for Jupyter, just by being web based.

The user should be able to do things as illustrated in picture below. This will facilitate quicker and more interactive data analysis, and also useful in cases where a full webviz instance is not needed.

Currently, the user is only represented with a standard __repr__ output:

Wanted output:

This can be achieved by giving the PageElement class a _repr_html_ method (which returns a html string) which is automatically found by Jupyter, and used as interactive output if available (instead of __repr__).

• Solve bug String representation of JSONPageElement not working #74.
• Add a _repr_html_ method, which is probably basically what __str__ is today (but without static resources like js-libs and css).
• Tell Jupyter about the static libraries to be included.