Make "docker insert" errors obvious

Closes #1130
See also #1942
Add ImageInsert tests
Merge pull request #2584 from dotcloud/docker-ci

docker-ci production sync
Merge pull request #2599 from dotcloud/prevent_panic_wrong_api_use

Prevent panic if you use API in a wrong way
Merge pull request #2597 from dotcloud/deprecate_separate_tag

Deprecate old tagging format
Merge pull request #2593 from dotcloud/2578

Fix mergeConfig with new ports
Merge pull request #2565 from danielnorberg/master

lock around read operations in graph
Merge pull request #9 from crosbymichael/fix-aufs-tests

Fix aufs error at startup
Do not remove mountpoint on umount
Implement changes for aufs driver
Name sure drivers are confined into their own dir
Merge pull request #10 from crosbymichael/aufs-fixes

Aufs fixes and driver dir namespaceing
Merge pull request #6 from alexlarsson/fix-ApplyLayer-remove

archive.ApplyLayer() remove files recursively
Use tmp dir in driver home
Make sure dirs are created before injecting file
Merge pull request #2526 from metalivedev/2074-AddKnownIssues

Add Known Issue
Add unit test for child changes diff in aufs
Return “err” instead of “nil” when MkdirAll() fails when binding a volume
Merge pull request #2610 from stapelberg/patch-1

Return “err” instead of “nil” when MkdirAll() fails when binding a volume
Removes duplicate changelog entry