CDB extension: Introduce StateNotificationBlocker.

Use RAI instead of manual bookkeeping when temporarily blocking
the state notifications of the extension context.

Change-Id: I991a3f0ddc578058f6bce173b4fc68ce567627ab
Reviewed-by: David Schulz <david.schulz@digia.com>
CDB extension: Introduce flags for exception handling to call command.

Change-Id: Ib913fe43755da16856c084e0ca72086dee596158
Reviewed-by: David Schulz <david.schulz@digia.com>
CDB extension: Add qmlstack command and helpers.

Add a command that dumps the QML stack. It tries to find
the address of the JS execution context in a complete stack
trace and calls the exported function in QML to create the
trace from it.

Task-number: QTCREATORBUG-11144

Change-Id: I8fef5df2b33b95748e78d837aba703945eaeead9
Reviewed-by: David Schulz <david.schulz@digia.com>