[ticket/11782] Change p.rules to p.post-notice in templates

PHPBB3-11782
[ticket/11782] Change p.rules to p.post-notice in CSS

PHPBB3-11782
[ticket/11782] RTL support for post notices

PHPBB3-11782
[ticket/11782] Apply line-height correctly

Apply line-height only to bolded elements inside post notices
that are direct child elements of forms.

PHPBB3-11782
Merge pull request #1651 from cyberalien/ticket/11782

Fix layout of notices in posts