Bug #1, Initial work on diagnostic quiz scaffolding

* https://github.com/IET-OU/oer-evidence-hub-org/issues/1
Fix and extend "simple_embed" WP plugin - "URL?comments=0"
Bug #1, fixes for "wp-juxtalearn-quiz" WP plugin - scaffolding etc.
Adding "slickquiz" and "wp-juxtalearn-quiz" WP plugins to Makefile

* TODO: add "slickquiz" to git submodules
Bug #1, Add "*_Quiz_Model" PHP and *-quiz-response Javascript/JS

* Branch: https://github.com/IET-OU/oer-evidence-hub-org/tree/quiz/CR1/scaffold
Add "jlq-loader"/ throbber CSS + Javascript/JS to scaffolding..

* Plus, fixed *-quiz-response JS
* Added Ajax PHP + JS to get stumbling blocks and student problems
Basic style/ CSS for quiz scaffolding
Add "start_time" etc. to *-quiz-response Javascript/JS

* Plus, JS Lint fixes.
Bug #2, Add facetious-hack Javascript - promote "post-type" search field

* Plus, other edits to "simple_embed" WP plugin etc.
Bug #1, Re-factored JuxtaLearn Quiz scaffolding into new PHP class

* Plus, moved embedded CSS to separate scaffold stylesheet
* Fixed "*-quiz-response.js" Javascript - I think
* API helper functions in *_Quiz_Model PHP class
Bug #3, Added "security_remove_wp_links()" - custom_functions PHP
Bug #1, Add *_Model::create_quiz_table(), save_score(), activate()

* ..To, JuxtaLearn Quiz WP plugin PHP classes
Bug #1, Add [quiz_score] short code

* Short code, required edits to core Quiz WP plugin and additions to model PHP
* Also, scaffold PHP and response Javascript
Bug #1, fix bug in JuxtaLearn_Quiz_Model::process_score() PHP
Bug #1, Add "radar-chart" d3 Javascript/JS, "quiz_score" shortcode mods

* Based on, Nadieh Bremer's work.
* http://bl.ocks.org/nbremer/6506614#RadarChart.js
Bug #3, Extend the "simple-embed" WP plugin stylesheet/ CSS

* For example, hide redundant page heading on quiz
Bug #1, Adding MSIE 8 warning message to "quiz_score" shortcode
Bug #3, Another CSS/stylesheet fix/ mod for "simple-embed" WP plugin
Bug #3, Add stumbling block names to *_Model::process_score()
Bug #1, Add <figcaption> to "quiz_score" visualization HTML

* Plus, fixed "null" axis in spider/radar diagram - ", {}" in Javascript