[ticket/11936] Fix Avatar overflow issue in Notification window

PHPBB3-11936
[ticket/11936] Restyle the notification text (no underline/decoration)

PHPBB3-11936
[ticket/11936] Use "no_avatar.gif" if needed in Notification window
[ticket/11936] Add no_avatars to UCP list Notifications too

PHPBB3-11936
[ticket/11936] Remove "px" from html syntax

PHPBB3-11936
[ticket/11936] Update no avatar image in Prosilver/Subsilver2

PHPBB3-11936
[ticket/11936] Make UCP Notifications page look even better

Make only the Notification Title/Text the href link. Use a font family
and size consistent with rest of phpBB. Make Notification date
smaller too.

PHPBB3-11936
[ticket/11936] Update the PM Notification Icon
[ticket/11936] Replace Notifications icon with a custom bell design

PHPBB3-11936
[ticket/11936] Additional Notification Bell Icon improvement

PHPBB3-11936
[ticket/11936] Merge branch 'develop' into ticket/11936

PHPBB3-11936
[ticket/11936] Update color scheme of new no_avatar.gif

PHPBB3-11936
Merge pull request #1789 from VSEphpbb/ticket/11936

[Ticket/11936] Notification Avatars - Fixes and Restyling