[ticket/10948] Separate color swatch cells.

PHPBB3-10948
Merge remote-tracking branch 'prototech/ticket/10948' into develop

* prototech/ticket/10948:
  [ticket/10948] Separate color swatch cells.
[ticket/11935] Fix invalid HTML usage of <label> tag in prosilver

PHPBB3-11935
[ticket/11935] Remove obsolete table attributes from Prosilver

cellpadding, cellspacing, border are obsolete table attributes.
They are handled by CSS already using table and .table1

PHPBB3-11935
[ticket/11935] Replace obsolete table attributes in Admin with CSS

PHPBB3-11935
[ticket/11935] Fix stray </a> tags

PHPBB3-11935
[ticket/11935] Fix incorrect alt tags that should be title tags

PHPBB3-11935
[ticket/11935] Fix <p> tags not allowed inside <strong> tags

PHPBB3-11935
Merge branch 'ticket/11935' of https://github.com/VSEphpbb/phpbb3 into ticket/11935