Bug 1085513 part1: Detect the mozconfig obj directory.

We cannot hardcode the object directory because it is configurable
inside the mozconfig file.

Parse the mozconfig and extract the object directory. If it is not
defined, defaults to "/home/worker/object-folder".
Bug 1085513 part2: use nightly mozconfig for b2g desktop builds.
Bug 1085513 part3: Remove unused mozconfig files.

Since we now use the gecko tree mozconfigs for building, the docker
mozconfigs are no longer necessary.
Update docker tester image to use gecko-tree base image
Merge pull request #6 from walac/bugz/1085513

Bug 1085513
Bug 1085511 part1: remove unused json files.

These were tasks in json format put here for tests. Not needed anymore,
kill them.
Bug 1085511 part2: add b2g desktop debug build task.
Merge pull request #8 from walac/bugz/1085511

Bug 1085511
Use worker for build tasks
Merge pull request #7 from rwood-moz/bug1090404

Update docker tester image to use gecko-tree base image
Merge pull request #10 from gregarndt/use_worker_user

Use worker for build tasks
Revert "Use worker for build tasks"
Merge pull request #11 from lightsofapollo/revert-10-use_worker_user

Revert "Use worker for build tasks"
Revert "Revert "Use worker for build tasks""
Merge pull request #12 from lightsofapollo/revert-11-revert-10-use_worker_user

Revert "Revert "Use worker for build tasks""
Bug 1085505 part1: Update tester image to create "artifacts" directory.

Artifacts are stored in the /home/worker/artifacts directory. If this
directory doesn't exist, the task finishes unsuccessfully.
Bug 1085505 part2: Add "create" and "deadline" fields in the template.

These fields are required for b2gtest tasks.
Bug 1085505 part3: Add the "ci-tests" mach command.

The --task-id cli allows you to pass the task id of the correspondent
build task. That's where the b2g image and test file are get from to
run the tests.
Merge pull request #13 from walac/bugz/1085505

Bug 1085505
Bug 1088232 - mach ci-docker-run