[ticket/9657] Populate data about post's delete status in mcp_post

PHPBB3-9657
[ticket/9657] Provide option to restore post in mcp_post

PHPBB3-9657
[ticket/9657] Fix typo in subsilver2 condition

PHPBB3-9657
[ticket/9657] Add note about post being soft deleted in subsilver2

PHPBB3-9657