Clean up shortcodes
Clean up shortcodes

Clean up the following:
* List group
* List group item
* List group item heading
* List group item text
Manually merge @nextgenthemes’ re-try at Nav Item

filipstefansson/bootstrap-3-shortcodes,filipstefansson/bootstrap-3-shortcodes,MWDelaney/bootstrap-3-shortcodes,MWDelaney/bootstrap-3-shortcodes,MWDelaney/bootstrap-3-shortcodes