Bump to 0.5.0

Make dockerfile docs easier to find. Clean up formatting.

Add unit tests for buildfile config instructions

Add tests for instructions in the buildfile that
modify the config of the resulting image.

*Runtime: improve docker rmi via id

Update docs with 0.5 repository information.

* Builder: Add verbose output to docker build

* Runtime: Merge -b and -v options

Always stop the opposite goroutine in network_proxy.go (closes #1213)

improve mergeconfig, ...

Hack: document PPA release step

Packaging: add pure binary to docker release

- Volumes: Copy VolumesRW values when using --volumes-from

* Runtime: Remove the os.user dependency and manually lookup /etc/passwd instead

Fixes #1201

Fix progressbar, without messing up other outputs

* RemoteAPI: Improve debug

Fixed tag option for "docker pull" (the option was ignored)

* Runtime: Reverse priority of tag lookup in TagStore.GetImage

Currently, if you have the following images:

    foo/bar      1       23b27d50fb49
    foo/bar      2       f2b86ec3fcc4

And you issue the following command:

    docker tag foo/bar:2 foo/bar latest

docker will tag the "wrong" image, because the image id for foo/bar:1 starts
with a "2". That is, you'll end up with the following:

    foo/bar      1       23b27d50fb49
    foo/bar      2       f2b86ec3fcc4
    foo/bar      latest  23b27d50fb49

This commit reverses the priority given to tags vs. image ids in the
construction `<user>/<repo>:<tagOrId>`, meaning that if a tag that is an exact
match for the specified `tagOrId`, it will be tagged in preference to an image
with an id that happens to start with the correct character sequence.

Keep debian package up-to-date

Packaging, issue #1202: Upgrade vagrantfile go in debian packaging