Add support for core field module "text"

UUID does not support translating the local IDs of entities embedded in filtered text fields. E.g., files embedded via the Media module, nodes embedded via node_embed, etc.

The UUID Link module provides a method for linking to content, but it does not replicate the functionality of Media module and other projects that embed content in filtered text fields.

To facilitate the deployment of filtered text fields with embedded entity tokens, I propose implementing hook_field_uuid_load() and hook_field_uuid_presave() for the core "text" field module in uuid.core.inc. i.e.,

  text_field_uuid_load($entity_type, $entity, $field, $instance, $langcode, &$items)
  text_field_uuid_presave($entity_type, $entity, $field, $instance, $langcode, &$items)

On their own, these hook implementations can not translate the embedded local entity IDs, because they don't know enough about the filtered text tokens of the projects that created them. Therefore, I propose two new hooks to allow projects to translate their embedded entity tokens from local ID to UUID. e.g.,

  hook_filtered_text_uuid_load_alter(&$text)
  hook_filtered_text_uuid_presave_alter(&$text)

If this approach and the following pseudo-code looks reasonable to the community/maintainers, I'll move forward with a patch.

text_field_uuid_load($entity_type, $entity, $field, $instance, $langcode, &$items)
  if instance is filtered text,
  then foreach $items
    drupal_alter "hook_filtered_text_uuid_load_alter(&$text)"
    hook implementation by input filter modules (media, node_embed, custom, etc.):
    - regex to find their token in $text
    - filter-specific logic to parse local ID from token
    - lookup UUID from local ID
    - make new token with UUID instead of local ID
    - str_replace old token with new token

text_field_uuid_presave($entity_type, $entity, $field, $instance, $langcode, &$items)
  if instance is filtered text,
  then foreach $items
    drupal_alter "hook_filtered_text_uuid_presave_alter(&$text)"
    hook implementation by input filter modules (media, node_embed, custom, etc.):
    - regex to find their token in $text
    - filter-specific logic to parse local ID from token
    - lookup local ID from UUID
    - make new token with local ID instead of UUID
    - str_replace old token with new token