* Log when we get a blocked numbers sync message
* Save three old signed keys in addition to the current active
* Remove the mystery from all the error-related log messages
* Log successful load of signed key - to help debug prekey errors
* removeSignedPreKey: Don't hang or crash in error cases
* Log on top-level unhandled promise rejection
* Remove trailing comma in param list, Electron 1.6 does not like
* Harden top-level error handler for strange object shapes