Common API usage documentation

Document the most important query functions to allow users to run custom queries without patching LDAP.

Example: I want to be able to provide a form of sorts to search for user who may or may not be in Drupal (I'd like it to search both Drupal users and LDAP users, based off their first name, last name, email address, or username). From that search, I'd like to give the ability to add a LDAP user to Drupal's user (if not already in Drupal's system).