Implement requested dynamic client capabilities.

* Implement a request to support loading clients from Couchbase doucments.
* Handles nested sections using new rlm_ldap code as an example.
* Complete Doxygen comments for all module structures and functions.
correct example view and change strn* functions to use the strl* counterparts
Merge pull request #810 from leprechau/couchbase_clients

Implement requested dynamic client capabilities in rlm_couchbase and document the new functionality.