Preprocess functions rename and documentation.

Changed the preprocess implementations to be prefixed with "template"
instead of the module name (see the second entry [here](https://api.drupal.org/api/drupal/includes!theme.inc/function/theme/7#sub_preprocess_templates)).
Additionally, updated the comments for the preprocess functions as per the
[standards](https://drupal.org/node/1354#themepreprocess).