[FEATURE] Add PDF thumbnail viewhelper
[TASK] Add "pdf" prefix to generated PDF thumbnails

This adds a dead-simple pdf prefix to the generated filename.
That way, one is able to simply delete all vhs-pdf-* files
from typo3temp without much hassle after fiddeling with ImageMagick
[BUGFIX] Correct order of included assets
Merge pull request #420 from bjo3rnf/assetorderfix

[BUGFIX] Correct order of included assets
Merge pull request #418 from bjo3rnf/pdfthumb

[FEATURE] Add PDF thumbnail viewhelper
[BUGFIX] LinkViewHelper should respect tag-content in translations

This fix postpones the title setting for sys_language_uid to the latest possible
point to overcome a bug.
Otherwise, the tag content wouldn't be taken into account when sys_language_uid != 0
Merge pull request #431 from cedricziel/pageLinkFix

[BUGFIX] LinkViewHelper should respect tag-content in translations