Backend: DummyDocSearch: add method predict_label_list() (to match DocSearch class)
Avoid a nasty exception when Paperwork starts

Signed-off-by: Jerome Flesch <jflesch@gmail.com>
Settings window: add links in the settings window to the wiki

Signed-off-by: Jerome Flesch <jflesch@gmail.com>
Merge branch 'stable' of github.com:jflesch/paperwork into stable