scriptworker: https://github.com/escapewindow/scriptworker signingscript: https://github.com/escapewindow/signingscript/tree/script

we will want to support 'try' key signing and production signing depending on props in the graph and the auth permissions of the graph creator. eventually, depending on whether the graph is part of the 'chain of trust' model

APK signing now works! See https://tools.taskcluster.net/task-inspector/#b_CA9TT8QrSuckBzOTEeSQ/ See https://bugzilla.mozilla.org/show_bug.cgi?id=1277579#c16 for a quick description of signingManifest vs task payload links. Whichever decision we make will be the route we go for both linux and android signing, and likely Windows and Mac too.

The work for setting up a task to handle signing has been done in bug 1277595. The format and key that we sign with is also configurable, but is currently hardcoded for fennec.