Issue #181 #182 Sandbox shutdown/termination

- Integrate the SandboxFilter shutdown with the Restarting interface changes
- Issue 181 now only applies to sandboxes after the Restarting interface was
added. The input channel is not closed until the matcher is done with it.
- Issue 182 on termination, new messages are recycled until the matcher is torn down
Simplify the recycle loop using range
Merge pull request #187 from mozilla-services/issue_182

Issue #181 #182 Sandbox shutdown/termination