cli integration tests

This is the initial code for the CLI integration tests based on Go's testing framework.

These tests don't remove, nor replace the current integration tests. This is an additional set of tests.

Things to be done:
- [x] integrate the tests into `hack/make.sh`
- [x] make sure `integration-cli` doesn't get executed by accident
- [x] make `docker_test_vars.go` read the variables from environment variables if they're defined
- [x] fix the Makefile and the scripts to use excludes, rather than hacks
- [x] added docker daemon logging and switched to pidfile
- [x] receive input from: @creack, @crosbymichael, @shykes, @tianon and @vieux
- [x] fix some issues with broken printing
- [x] decide if dropping Go testing and switching to a standalone binary would be a good idea
- [ ] clean up and refactor the code based on input
- [ ] figure out how to handle timeouts
- [ ] add more needed functions to utils
- [ ] set up registry handling
- [ ] tests for the utilities used for the tests