Add option to 'remove class cruft'

[stevetweeddale]

Generally, the nicer the CSS, the less 'standard' css classes we'll use. So ideally we'll like to be able to remove all those default classes from things. D8 goes a long way toward this (choose the classy base theme if you want the classes) but in D7 we're kind of on our own.

So we normally would remove them in a preprocess. Oftentimes that means we end up with something like this:

$variables['classes_array'] = array();

… before then adding just the nice custom classes we want. Whilst this is tempting because it's quick and easy to get a 'clean slate', it's a pretty nuclear solution, and totally breaks certain things (such as contextual links regions).

A nicer way would be to methodically remove all the uber-generic crufty classes we don't want eg. for paragraphs:

  cm_tools_array_remove_values($variables['classes_array'], array(
    'entity',
    'entity-paragraphs-item',
    'paragraphs-item-' . drupal_clean_css_identifier($variables['elements']['#entity']->bundle),
    'paragraphs-item-' . $variables['view_mode'],
    'paragraphs-item-' . drupal_clean_css_identifier($variables['elements']['#entity']->bundle) . '-' . $variables['view_mode'],
  ));

… but as you can see that's a long way from quick and easy.

So, the suggestion is we have a global opt-in setting for cm_tools that just does this for common theme hooks (preprocesses away the stock classes). We'll need to module_implements_alter each of our preprocess functions to be late (specifically, later than whatever module defines the hook).

[darthsteven]

Looks good to me! Resolve the conflict, and we're good to merge!