First leg of Yifi search, still unplugged. Now search results may have a thumbnail url.
refactored getThumbnailUrl() default implementations into abstract parent. duh
should fetch best available thumbnail image from youtube
We have Yifi results.
Split 'common/' into commit 'd27a7879fba2163f838a25db9472a260dac7039c'

git-subtree-dir: common
git-subtree-mainline: db3cc3d3c0ee0ac9607d18db5ba465a6bbf7ca52
git-subtree-split: d27a7879fba2163f838a25db9472a260dac7039c