[ticket/11626] Create get_acp_template method for auth providers

PHPBB3-11626
[ticket/11626] LDAP Auth ACP Template File

PHPBB3-11626
[ticket/11626] Include the template file in acp_board

PHPBB3-11626
[ticket/11626] Change interface to match functionality

Changes the interface so that it matches the new functionality of
phpbb_provider_auth_interface::acp().

PHPBB3-11626
[ticket/11626] Call method only one time per provider

PHPBB3-11626
[ticket/11626] Change the identifier template file in the template

PHPBB3-11626
[ticket/11626] Make identifier uppercase per style requirements

PHPBB3-11626
[ticket/11626] Remove LDAP dependency on template

Returns template vars rather than requiring the template.

PHPBB3-11626
[ticket/11626] Remove last reference to template in ldap

PHPBB3-11626
Merge remote-tracking branch 'remotes/Hardolaf/ticket/11626' into develop

# By Joseph Warner
# Via Joseph Warner
* remotes/Hardolaf/ticket/11626:
  [ticket/11626] Remove last reference to template in ldap
  [ticket/11626] Remove LDAP dependency on template
  [ticket/11626] Make identifier uppercase per style requirements
  [ticket/11626] Change the identifier template file in the template
  [ticket/11626] Call method only one time per provider
  [ticket/11626] Change interface to match functionality
  [ticket/11626] Include the template file in acp_board
  [ticket/11626] LDAP Auth ACP Template File
  [ticket/11626] Create get_acp_template method for auth providers