Finishing some todos and fixing some bugs

navigation MDL-20276 Fixed up the navigation for the quiz module and question section as per Tim's recommendation.
* Routine navigation through the quiz and question modules
* Fixed navbar through quiz and questions
* Pages headers added throughout
* Added method to turn a navigation node into a tabs array suitable for use with print tabs

MDL-20296 modifications necessary for improving grading for numerical and transform display.html as independent from
shortanswer, add display of unitpenalty for numerical in print_question_grading_details()

MDL-20296 improving grading for numerical and transform display.html as independent of the analoguous shortanswer file

MDL-20296 improving grading for numerical and transform diplay.html as independent of the analoguous shortanswer file

MDL-20296 creating common functions to handle units in numerical, calculated and calculatedsimple edit forms
and improving grading and rendering

MDL-20296 creating common functions to handle units in numerical, calculated and calculatedsimple edit forms

MDL-20296 creating common functions to handle units in numerical, calculated and calculatedsimple edit forms

Removing access to $PAGE from this function