add configurable setting to section_links block for the increment by and number of secitons that are hardcored

Added the 4 new settings for the section_links block to allow the site administrator to determine the number of sections that will be displayed before the sections are incremented by more than 1. At the moment this is hard coded at 22 by 2 and 40 by 5.

This is a pretty quick patch, the descriptions could use some work, and it might be good to make this a block configuration as well as a site configuration to allow instructors to edit the section links on a course by course basis.

Jason Hardin