Squashed 'app/' changes from d19f26d..f809920

f809920 Added optional proposition variable to header

git-subtree-dir: app
git-subtree-split: f809920a37cdbbc40dda9c077d570b4e9f399b22
Merge commit 'eb512e0c113d85990778e0275a0d6b25f5a77926'