[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/12063] Remove obsolete valign attributes from tr tags

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

PHPBB3-12064
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/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