Engine: integer job status, improved stream API

* Jobs return an integer status instead of a string
* Status convention mimics unix process execution: 0=success, 1=generic error, 127="no such command"
* Stdout and Stderr support multiple thread-safe data receivers and ring buffer filtering
Engine: new command 'stop' gracefully stops a container.
move t from arg to env
Add -bip flag: allow specification of dynamic bridge IP via CIDR

e.g.:

```
docker -d -bip "10.10.0.1/16"
```

If set and valid, use provided in place of trial and error from pre-defined array in network.go.
Mutually exclusive of -b option.
Merge branch 'libvirt-prereq-network' of https://github.com/jpoimboe/docker
Merge branch 'master' of https://github.com/dotcloud/docker
fix #3141 Bridge creation when ipv6 is not enabled
Add new cover bundlescript for giving a nice report across all the coverprofiles generated by the test scripts
Merge branch 'master' of https://github.com/dotcloud/docker
Merge pull request #3211 from tianon/hack-make-cover

Add new cover bundlescript for giving a nice report across all the coverprofiles
Fix #1695 by adding more about logging.
Merge pull request #3210 from rsampaio/fix_bridge_creation_3141

Bridge creation when ipv6 is not enabled
Merge branch 'master' of https://github.com/dotcloud/docker
move resize to job
Temporarily remve @shykes from engine/MAINTAINERS
Merge pull request #3187 from vieux/resize_job

Move resize to job
Merge pull request #3208 from WarheadsSE/bridgeip

Add -bip flag: allow specification of dynamic bridge IP via CIDR
Merge pull request #3214 from dotcloud/shykes_maintainer

Temporarily remove @shykes from engine/MAINTAINERS
Merge pull request #3175 from vieux/engine-job-stop

Move stop to job
Merge pull request #3213 from metalivedev/1695-dockerlogs

Add more information about Docker logging