Chained response actions should all be run, even if one fails

When an Ajax response is received with more than one action, all of them should
be run, even if one of them fails.

This will require a spec clarification.

However - what happens to the client event model in this case?

If we have three actions, and the second fails, we should probably generate the
error event. But what if all three fail? Or only the first two? The user
would be responsible for doing error handling - but they wouldn't know which
succeeded, and which failed. Generating more than one error event may be the
way to go here, I'll have to think about it further.

This would be more clearly handled with a new event type: see spec #678 for
more.
#### Environment
Operating System: All
Platform: All
#### Affected Versions
[2.0]

Start with the spec clarification requested in this issue and read spec #678, then examine the existing Ajax response-action and client event behavior. Resolve how failures and error events should be reported when multiple actions are chained, and define the resulting specification and implementation scope; no file or test is named here.

Written by the indexing model from the issue text.