[ticket/12563] Changes 2 language variables to better understandable names

PHPBB3-12563
[ticket/12563] Removes strintf in acp_styles.php and shorts up <a>

PHPBB3-12563
[ticket/12563] Removes ending . from <a>

PHPBB3-12563
[ticket/12608] Improve notifications drop-down menu styling in header

PHPBB3-12608
[ticket/12608] Updated tests

PHPBB3-12608
[ticket/12608] Add styling (CSS class) options to notifications

This will allow different notifications to have different styles

PHPBB3-12608
[ticket/12608] Clean up whitespace

PHPBB3-12608
[ticket/12608] Improved LTR and various bugfixes

PHPBB3-12608
[ticket/12608] Remove somewhat redundant reported color style

PHPBB3-12608
[ticket/12608] Changed get_styling() to get_style_class()

PHPBB3-12608
[ticket/12608] Add subSilver

PHPBB3-12608
[ticket/12728] Enforce box model sizing on image attachment thumbnails

PHPBB3-12728
[ticket/12612] Move functions from posting.php to functions_posting.php

PHPBB3-12612
[ticket/12612] Move functions from memberlist.php to functions_display.php

PHPBB3-12612
[ticket/12612] Move function from ucp.php to functions_user.php

PHPBB3-12612
[ticket/12612] Move functions from mcp.php to functions_mcp.php

PHPBB3-12612
[ticket/12747] Drop support for Firebird

PHPBB3-12747
[ticket/12704] Improve the load time information in the footer when enabled

PR #2570 has added new constant to display load time information without
debug mode is being on (https://tracker.phpbb.com/browse/PHPBB3-12687).
This patch expands the total load time info with SQL/PHP load times,
while hiding the additional info with <abbr> element.

PHPBB3-12704
[ticket/12747] Remove some methods which are not used anymore

PHPBB3-12747
[ticket/12728] Adjust .postimage sizing to 100%

PHPBB3-12728