Make dashboard more mobile friendly in 5.6.x

Re-adding viewport in whole dashboard, some tweaks in mobile.less
Make the asset helper easier to use

When using the asset library helper, it expects a file object for the existing file. Yet files are usually saved as file IDs. 

Making the helper adapt to accept an object or ID for the existing file saves anyone using the library from having to worry about the difference.
use mysql compatible date format
remove *1000
date helper
date helper fix
Fix handling not existent images with ImageMagick

Execution dies if ImageMagick can't load an image: let's return false if
we can't load/process the image (plus let's free GD handles).
Fix PHPDoc

Let's describe better the create method...
Fix PHPDoc

State in the docs that the create method will only downsize the original image
convert date in $_REQUEST to proper timestamp
500 on validate_user_email.php tool

This file is no longer used anywhere in the core, and calling it (no matter what parameters) will cause an Internal Server error because UserInfo::validateUserEmailAddress() does not exist
make sure we only install new blocks
Remove check against user-agent

Multiple file upload uses SWFUpload, which uses a different user-agent
fixed problem with email validation vs size of email field that would allow a user to enter an invalid email if it was over the size of the email field (64)
fixed the 5631 version helper
Don't show that a page is pending approval unless they can view the toolbar
Allow apostrophes in page control menus attribs

Translations may contain apostrophes, but this would break the resulting
JavaScript.
Let's encode those strings with json_encode...
Fix deleting aliased page

Let's remove the alias when we call the delete method on an alias
Move alias page instead of original original page
Let's fallback to GD if ImageMagick fails