adding configuration page and a few options

[choldgraf]

Decided to refresh myself on how to use variables in themes :-)

This does the following:

• Adds a theme option to show/hide the "previous/next" buttons
• Adds a theme option to include social media icons that point to configurable URLs
• Adds FontAwesome CSS (which fixes the broken social media icon links)
• Adds a theme option to add external links
• Adds content to the configuration page for each of these things

[jorisvandenbossche]

Thanks a lot for this!

[jorisvandenbossche]

Could also be a tuples of (name, url), but the dict is also good for me (and a dict is more easily extendable, if needed in the future).

[jorisvandenbossche]

And I suppose the dict is also nicer to use in the jinja layout

[choldgraf]

yeah I was thinking a dict because it'll be more obvious in the templates

[jorisvandenbossche]

For the font-awesome noob: what is this doing?

[choldgraf]

this is the unicode version of a fontawesome icon. FontAwesome is a standard icon pack that you can load via CDN and then use for icons on your site. The Bokeh docs are using fontawesome for their github / twitter logos so I figured we can just copy the same pattern here

[choldgraf]

I updated the fontawesome bits to use <i> instead of the unicode CSS hack, since that's what they recommend. Also upgraded to FA5 per @stijnvanhoey's suggestion.