Make CKEditor bulletproof against js errors

[Frederico Caldeira Knabben]

To start, let's state that there are so many variables on the editor usage, which makes it impossible to predict every single case. Because of this, the editor fails with js errors from time to time.

We could have a system in place, to protect users from js errors. The basic idea would be based on a simple "job system":

1. A job is started by code.
2. If an error happens during the job life-cycle:
   1. The editor status is reverted to the "before job" state.
   2. The error is reported to the user.
   3. It would be nice to have a way to the user to send the report to us, including their editor configuration, data and selection before job start and details about the job.
3. The job is finished by code.

The system must support asynchronous operations within the job (setTimeout calls, load of external files, etc).

One idea is integrating this system into the undo system transparently, so it would always revert to the previous undo snapshot in case of errors.

[Jakub Ś]

Since "is null" errors occur from CKEditor 3.0 this is the version I'm setting.