Updated some comment elements and standardised more JS

Updated some comment elements and standardised more JS

- Updated comment routes to be simpler.
- Updated comments JS to align better with updated component system.
- Documented available global JS functions/services.
- Removed redundant controller method.
- Added window.$events helpers for validation messages and
success/error.
- Updated JS events system to not be class based for simplicity.
- Added window.trans_plural method to handle pluralisation/replacements
where you already have the translation string itself.

Fixes #1836