Use URI instead of String in tracking visited files #1544
Use URI instead of String in merge utils #1544
Use File instead of String #1544
Refactor to make code more simple
Clean PDF stylesheets
Add support for back cover generation on PDF #1671
Add template for front cover contents in PDF
Remove DITA 1.0 specific processing from PDF
Remove commented out code in PDF
Convert tabs to spaces in PDF XSLT and XML files
Merge commit '231dd3ceab2ce3d53247c544019a1b6164b95ddf' into develop