Make "docker insert" errors obvious

Closes #1130
See also #1942
Add ImageInsert tests
Update release script with proper support for non-*.docker.io bucket URLs
Update release script to move https://get.docker.io/ubuntu/info to https://get.docker.io/ubuntu/ and provide a backwards-compatibility redirect (same for /builds/info)
prevent deletion if image is used by a running container
Fix the display of get.docker.io in Firefox by making our index files text/plain
Edits after code review

Return long image ID
Return streamformatted error or "raw" error
Make sure docker kill exit with failure in case of error
Just return the id; nothing else.
use utils.ParseRepositoryTag instead of strings.split in docker images
add wait, stop, start, restart, rm, rmi
on docker start, do not cleanup if already running
fix nameserver regex.
modify test of GetNameserversAsCIDR for its regex change.
Merge branch 'tests/insert' of https://github.com/mrallen1/docker into mrallen1-tests/insert

Conflicts:
	server.go
Add clarification of multiple "go test" calls in hack/make/*test
Merge pull request #2669 from tianon/clarify-test-calls

Add clarification of multiple "go test" calls in hack/make/*test
Merge pull request #2657 from dotcloud/fix_docker_images_output

use utils.ParseRepositoryTag instead of strings.split in docker images
Merge pull request #2614 from dotcloud/prevent_delete_image_running_container

Runtime: prevent deletion if image is used by a running container
Merge pull request #2662 from dotcloud/do_not_cleanup_start_if_running

on docker start, do not cleanup if already running