Update to 5.7.4.2

* Update MESSAGES.

Changelog:
5.7.4.2

Behavioral Improvements

    Saving only a custom template on a block will no longer wrap that block in a custom design DIV. Better saving and resetting of custom designs on blocks and areas.
    Topics improvements: topics can now be created below other topics; the only different between topic categories and topics is that categories cannot be assigned to objects, only topics can.
    We now include the page ID in the attributes dialog and panel.
    Feature block now contains an instance of the rich text editor (thanks MrKarlDilkington)
    Improvements to new update functionality when site can't connect to concrete5.org
    Improvements to new update functionality to make it more resilient with failures, but error messaging.
    Adding attributes to a page will ask for it be checked back/approved when clicking the green icon.
    Theme name and description can now be translated (thanks mlocati)
    Added an error notice when deleting a page type that窶冱 in use in your site.

Bug Fixes

    Some servers would redirect infinitely when activating a theme or attempting to logout. This has been fixed.
    Fix bug with multiple redactor instances on the same page and in the same composer window causing problems.
    Better rendering of empty areas in Firefox (thanks JeramyNS)
    Fixed problems with 窶彡oncrete.seo.trailing_slash窶� set to true leading to an inability to login, other problems.
    Attributes that had already been filled out were being shown as still required in page check-in panel.
    Fixed bug where full URLs were incorrectly parsed if asset caching was enabled (thanks mlocati)
    Fix download file script leading to 404 errors after you go to the dashboard and hit the back button
    Fixed https://www.concrete5.org/developers/bugs/5-7-4-1/dont-allow-to-create-file-sets-with-names-containing-forbidden-c/
    Fix https://www.concrete5.org/developers/bugs/5-7-4-1/cant-replace-a-file-with-one-in-the-incoming-directory/
    Fix XSS in conversation author object; fix author name not showing if a user didn't put in a website (thanks jaromirdalecky)
    Searching files, pages and users by topics now works in the dashboard
    Picture tag now properly inserted by Redactor when working with themes that use responsive images.
    Fixed z-index of message author and status in conversations dashboard page.

Developer Updates

    API improvements to the RedactorEditor class.

And many improvements and bugfixes including security bugfixes.

(ryoon)