[ticket/11716] Convert Soft Delete Mod to post/topic visibility

PHPBB3-11716
[ticket/11716] Rename migration files and add note that it's converting a MOD

PHPBB3-11716
[ticket/12176] Add functional test for founder deletion message.

PHPBB3-12176
[ticket/12176] Display correct message when trying to delete founder.

PHPBB3-12176
[ticket/12244] Rename link to Extensions Manager in the ACP

PHPBB3-12244
[ticket/8785] Rebuilding posting_editor pm head + new language vars

PHPBB3-8785
[ticket/8785] Little spaces mistake

PHPBB3-8785
[ticket/8785] Scrollbar to Reciepients and BCC with max-height: 200px

PHPBB3-8785
[ticket/8785] Adds two <hr /> to seperate recipients and BCC

PHPBB3-8785
[ticket/8785] Adds a new optical improvement, new file and fixes html bugs

PHPBB3-8785
[ticket/8785] Adds blank lines at file end

PHPBB3-8785
[ticket/8785] <hr /> will only displayed when needed

PHPBB3-8785
[ticket/8785] pm_layout.html back to more standard code

PHPBB3-8785
[ticket/8785] Just one blank line

PHPBB3-8785
[ticket/8785] and again a fresh line

PHPBB3-8785
[ticket/8785] Fixed problem with add empty.png and travis will now pass

PHPBB3-8785
[ticket/12261] Remove web root path from login redirect url

The redirect url must be relative to the ucp.php and not relative to the
current page.

PHPBB3-12261
[ticket/12261] Add a functional test for redirect after using login_box()

PHPBB3-12261
[ticket/12261] Validate the redirect hidden field before submitting the form

PHPBB3-12261
[ticket/12261] Fix doc block

PHPBB3-12261