Bug #9, JuxtaLearn - custom style/CSS for a menu link to ClipIt

* WordPress:  add_action( 'wp_head', .. 'head_custom_style' )
Bug #8, A big re-work of the JuxtaLearn ClipIt API plugin

* Implemented WP action, "save_post"
* Moved authentication to "JuxtaLearn_ClipIt_Auth" class
Updating submodule "wp-juxtalearn-hub" from 11 March to 6 May

* https://github.com/IET-OU/wp-juxtalearn-hub/commit/35d85342241dcc0d
Merge branch 'juxtalearn' into jxl/CR8/api