Update docs/source/interactive/htmlnotebook.txt

Added a section on configuration. Still need to add a link to the general configuration page.
Update docs/source/interactive/htmlnotebook.txt

Added links to IPython configuration page.
Update docs/source/interactive/htmlnotebook.txt

edited as per suggestions in pull request
Merge pull request #2915 from drevicko/patch-1

added small config section to notebook docs page