replace close button

Conflicts:
	files_pdfviewer/templates/pdf.php
download button misteriously disapeared

Conflicts:
	files_pdfviewer/templates/pdf.php
dnld button

Conflicts:
	files_pdfviewer/templates/pdf.php
Merge pull request #1202 from owncloud/backport_pdf-closebutton

Backport pdf closebutton