Rough out the package structure

Create an approximate set of packages for the guardian backend. These
can be refactored as necessary.

Copy earlier work from cf-guardian/guardian and cf-guardian/prototype.

Some policy decisions in the earlier work may need to be revisited:
* gerror for error creation
* glog for logging

New packages:
* collecting for managing multiple containers
* config_builder for building libcontainer container config
* warden_config to encapsulate backend's config file
* gb_init_process initial process main (a.k.a. son of wshd)
* rootfs for building layered root file system
* temp_libcontainer_api until we have an agreed API to libcontainer
Merge branch 'master' into structure

* master:
  Bring in README.md (with mods) from guardian.  Also development/scripts from same, and LICENSE file for the pre-commit hook.
  Fix compile errors
  Factor out signal handler into utils
  Factor out exit code
update mock_fileutils
Merge branch 'master' into structure

* master:
  Oops: move new README to top level!
Update mocks.
Merge branch 'master' into structure

* master:
  Fix some code block formatting issues.
update update_mocks
Remove all references to cf-guardian/guardian/.
Move to use private version of libcontainer API.
Fix files to compile and test.