pulled method relying on user session from the base into the web controller.
renamed method  more aptly.
added proper doc block.
simplified method implementation.
renamed user preferences option in views-data array. JSON encoded array in the controller, rather than awkwardly doing it in the view templates.
added new includes template for setting the instantiating the client-side user preferences model.
removed text value evaluation since the input is expected to be boolean now. updated doc block.
removed unnecessary client side user preferences model instantiation.
removed unnecessary user pref. retrieval from index action.
changed wrapping quotes to double quotes since the given JSON string escapes double quotes, not single quotes.
replaced per page-level template crap with common include.
removed obsolete call to ilios.global.installPreferencesModel().
Merge pull request #403 from stopfstedt/this-is-annoying-me-so-much

reworked data flow for user preferences from server to client side.