remove boilerplate.css

it is redundant with bootstrap reset
add IPython-only CSS

adds static/style/ipython.less and ipython.min.css

Which should contain minimal styling that conflicts with other CSS.

As we improve our CSS scoping and naming,
this file should eventually be enough to play nice with embedding IPython in other HTML contexts.
move font-awesome to style.less from notebook-specific less

allows it to be excluded from ipython.min.css,
where it doesn't make much sense.
Merge pull request #3630 from minrk/css

CSS adjustments

- remove boilerplate.css, as it is redundant with bootstrap's own reset.less
- add ipython.less / ipython.min.css for IPython-only CSS
- move font-awesome to outermost style.less, so it is not included in ipython.min.css,
  where it is not desirable.

This doesn't do any of the naming / scoping cleanup that we should ultimately do, but it does create the file where that will have its desired effect.