Sidebar

Hey,

Here is the implementation of the sidebar i have been using.

I also added some configuration options to disable the sidebarrel and pagenav, since the user may want to define their own in the sidebar.

FYI, I didn't see the #33 until after I had finished making this pull request.  His sidebar looks far more advanced, but it also is more complex. I probably don't have time at the moment to port all of the functionality.  But i have no problem if you would like to delay merging this to instead focus on extracting the other sidebar.

Cheers,
Russell