Refactoring (mostly rewritten). Introducing new classes Sympa::Request::Handler::include, Sympa::DataSource and its subclasses. Sympa::Datasource was deprecated.

And some fixes:
  * [bug] Now include_remote_file, include_sympa_list and include_remote_sympa_list paragraphs may have nosync_time_ranges subparameter.  No reason they don't have it.  include_file stil doesn't have it.
  * [-feature] include_voot_group has not been implemented, and it was invalidated.
  * [bug] include_ldap_query and include_ldap_ca data sources did not implement "regex" option of "selection" subparameter.  Now they support it.
  * [bug] LDAP multiple values in custom attribute with include_ldap_ca was broken.
  * [-feature] include_sql_query and include_sql_ca stores inclusion data in temporary file so that big data sources will be handled safely.

Tentative change:
  * include_ldap_query, include_ldap_2level and include_sql_query won't clear (overwrite) gecos if retrieved value was empty or undefined.  Now they clear (overwrite) gecos in such cases.