In R1.6 the link between extension and app-to-start is not fixed anymore in the ctb. See
here in the Xournal thread for a quick way to link entensions to an application.
It 're-uses' the newpaper entry. There is also a way to add new filetypes, but I am not sure how safe that is. I currently use the newspaper to link some documents to FBreader like this:
Code:
/apps/er/sys/ctb/filetypes/doc-newspaper/descr=Newspaper
/apps/er/sys/ctb/filetypes/doc-newspaper/icon_name=newspaper
/apps/er/sys/ctb/filetypes/doc-newspaper/template_descr=Newspaper Template
/apps/er/sys/ctb/filetypes/doc-newspaper/extensions=htm;html;xhtml;chm;fb2;
/apps/er/sys/ctb/filetypes/doc-newspaper/viewer_cmd=/media/mmcblk0p1/Programs/_fbreader/bin/FBReader
I am not sure if I got all extensions.