[ticket/11859] Make avatar drivers return template filename

The service name might not follow the expected naming scheme which would
cause abnormally long filenames and confusion for authors that might add
more avatar drivers.

PHPBB3-11859
[ticket/11859] Add missing get_template_name method to test drivers

PHPBB3-11859
[ticket/12054] Update index_body_linklist_before/after template events

PHPBB3-12054
[ticket/12063] Remove obsolete valign attributes from tr tags

PHPBB3-12063
[ticket/12064] Delete obsolete viewsource.html file from adm/style/

PHPBB3-12064
[ticket/12009] Do not allow incorrectly structured extensions to be installed.

PHPBB3-12009
Merge remote-tracking branch 'Marc/ticket/11859' into develop

* Marc/ticket/11859:
  [ticket/11859] Add missing get_template_name method to test drivers
  [ticket/11859] Make avatar drivers return template filename
Merge remote-tracking branch 'vsephpbb/ticket/12064' into develop

* vsephpbb/ticket/12064:
  [ticket/12064] Delete obsolete viewsource.html file from adm/style/
[ticket/10023] Make password change notification more noticeable

PHPBB3-10023
[ticket/12054] Reword descriptions and resort events alphabetically

PHPBB3-12054
[ticket/12009] Move valid extensions in tests to correct dir structure.

PHPBB3-12009
[ticket/12009] Fix functional tests.

PHPBB3-12009
[ticket/12009] Update functional test to check for invalid extensions.

PHPBB3-12009
[ticket/12009] Prevent user from enabling invalid extension through direct URL

PHPBB3-12009
[ticket/12063] Use CSS to replace valign=top

PHPBB3-12063
Merge remote-tracking branch 'vsephpbb/ticket/12063' into develop

* vsephpbb/ticket/12063:
  [ticket/12063] Use CSS to replace valign=top
  [ticket/12063] Remove obsolete valign attributes from tr tags
[ticket/12054] Re-word event documentation

PHPBB3-12054
Merge remote-tracking branch 'vsephpbb/ticket/12054' into develop

* vsephpbb/ticket/12054:
  [ticket/12054] Re-word event documentation
  [ticket/12054] Reword descriptions and resort events alphabetically
  [ticket/12054] Update index_body_linklist_before/after template events
Merge remote-tracking branch 'prototech/ticket/12009' into develop

* prototech/ticket/12009:
  [ticket/12009] Prevent user from enabling invalid extension through direct URL
  [ticket/12009] Update functional test to check for invalid extensions.
  [ticket/12009] Fix functional tests.
  [ticket/12009] Move valid extensions in tests to correct dir structure.
  [ticket/12009] Do not allow incorrectly structured extensions to be installed.
Merge remote-tracking branch 'Elsensee/ticket/10023' into develop-olympus

* Elsensee/ticket/10023:
  [ticket/10023] Make password change notification more noticeable