fixes for picdocument
fixes for picdocument

picdocument didn't use the document API correctly

NiLuJe/koreader,poire-z/koreader,NiLuJe/koreader,Frenzie/koreader,noname007/koreader,mihailim/koreader,Hzj-jie/koreader,Frenzie/koreader,ashhher3/koreader,koreader/koreader,chrox/koreader,frankyifei/koreader,houqp/koreader,chihyang/koreader,mwoz123/koreader,poire-z/koreader,koreader/koreader,robert00s/koreader,Markismus/koreader,apletnev/koreader,lgeek/koreader,pazos/koreader,NickSavage/koreader,ashang/koreader