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.
Suppress errors for setcookie and session_start in user model

Occured if output was already sent (e.g. with install script)
use mysql compatible date format
get area handle and name through method which is easier to override
fix theme name in tinymce plugin translations
Revert "get area handle and name through method which is easier to override"

This reverts commit 02d027478f61968632bfed630b70cc62f6a9d21f.
translations for simple theme added
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
fix phpass breaking install on open basedir
Merge pull request #1673 from Nkay/phpassfix

fix phpass breaking install on open basedir
convert date in $_REQUEST to proper timestamp
check if job is already installed
make sure we don't get a result like my-page/?&var=value
Merge pull request #1664 from worldskills/fix-install-concrete5

Suppress warnings for setcookie and session_start in user model