LMS: revising Student Notes FED, UI, and visual styling

* revising notes view styling scope to use a <body> class
* revising HTML basics: indentation levels, button UI classes, view-level styling and semantics
* basic Sass/CSS clean up
* deeper Sass/CSS clean up + abstraction
* typography syncing
* refining and defining notes visual color
* changing reference heading copy
* revising Student Notes visual styling
* revising no search results styling/UI
* revising search error styling/UI