Squashed 'static/js/grid/' changes from cfdb6ca..b7d09e7

b7d09e7 Merge branch 'master' into subtreeable
6c9800a Improve data check

git-subtree-dir: static/js/grid
git-subtree-split: b7d09e71b5000a756bc105e9701793db36080289
Merge commit 'c38c693bc39263b8b957c829fc43a410d0185a08'
Remove useless placeholder in HTML form
Fix status for websites which have never been checked
Fix display for websites which have never been down
Use the grid component to show websites downtimes
Improve exception handling