Change serf version to 4 so the entire test suite doesn't fail

Added logging to server startup so we can see where it fails

API client package

Config merging

Add docker resource constraints for CPU and Memory

Added config to drivers; needed for docker driver to get the socket endpoint

Conflicts:
	client/driver/driver.go

Replace logging and config with DriverContext, which allows us to expand the dependency injection without changing the interface

Basic Qemu driver implementation 

Change SIGINT to SIGTERM

- Add validation that Resources.MemoryMB and Resources.CPU have non-zero values
- Change log calls to use logger whenever possible
- Change log format to add colon after driver.docker