Revert "Issue #112: added navigation.html to html_sidebars settings"
Revert "Issue #112: added navigation.html to html_sidebars settings"

This reverts commit 9c6f2b6aad8e7ae3b5ac0e487139c9d2d082680e.

NifTK/NiftyNet,NifTK/NiftyNet,NifTK/NiftyNet,NifTK/NiftyNet