add show/shown hide/hidden events to dropdown + update dropdown links for testing + catch a few missed namespace things

Use base padding for input-group-addon class

I reworked the customizer to match the new docs layout and include all
newly added variables, etc.
Would be glad to keep an eye on Customize and update it as v3 changes.
Help blocks in my new version need some more work, too, so this is just
a basis.

Fixed broken Customizer link for docs

* Remove notes on repo section
* Update hirearchy of coding standards sections

* No more negative side margins
* However, keep the negative margin for nested rows

* No more children selectors to set all links in alerts as a special color because buttons and more wrongly inherited color
* Adds .alert-link for easy styling in any alert

* changed .row-label to .control-label as used elsewhere already
* changed .formFieldState mixin to .form-field-validation