DocumentViewer(+FontPack): Fix build

Closed username-removed-85639 requested to merge (removed):DocumentViewer into master

Document Viewer Font Pack now uses gradle

Document Viewer has MuPDF as a git-submodule and needs to run some commands from a script. Is posible to run them directly ( pushd jni/mupdf/mupdf && make generate && cd .. && patch -p1 -d mupdf < overrides/nightmode_slowcmyk.patch && popd ), but i think that is better for the AUM to just run the script