[backend] also cache nonexisting players
[options] fixed typo
[project] added Sugar.js

Replaced all `if (a in b)`, `for (a in b)`, `a.indexOf(b) === -1`, and poor
attempts at capitalisation with the right sugar.js calls
[options] fixed bug where manifests couldn't be removed

due to the latest relayouting of the options page, the jQuery code didn't
work anymore