Add basic logging to file support

This currently logs to a json file with the stream type.  This is slow
and hard on the cpu and memory so we need to swich this over to
something like protobufs for the binary logs but this is just a start.

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

runtime/runtime.go

@@ -7,18 +7,20 @@ import (
 )
 
 var (
-	ErrNotChildProcess      = errors.New("containerd: not a child process for container")
-	ErrInvalidContainerType = errors.New("containerd: invalid container type for runtime")
-	ErrCheckpointNotExists  = errors.New("containerd: checkpoint does not exist for container")
-	ErrCheckpointExists     = errors.New("containerd: checkpoint already exists")
-	ErrContainerExited      = errors.New("containerd: container has exited")
+	ErrNotChildProcess       = errors.New("containerd: not a child process for container")
+	ErrInvalidContainerType  = errors.New("containerd: invalid container type for runtime")
+	ErrCheckpointNotExists   = errors.New("containerd: checkpoint does not exist for container")
+	ErrCheckpointExists      = errors.New("containerd: checkpoint already exists")
+	ErrContainerExited       = errors.New("containerd: container has exited")
+	ErrTerminalsNotSupported = errors.New("containerd: terminals are not supported for runtime")
 )
 
 // Runtime handles containers, containers handle their own actions
 type Runtime interface {
-	// Create creates a new container initialized but without it starting it
-	Create(id, bundlePath string, stdio *Stdio) (Container, error)
-	// StartProcess adds a new process to the container
-	StartProcess(Container, specs.Process, *Stdio) (Process, error)
+	// Type of the runtime
 	Type() string
+	// Create creates a new container initialized but without it starting it
+	Create(id, bundlePath string) (Container, *IO, error)
+	// StartProcess adds a new process to the container
+	StartProcess(Container, specs.Process) (Process, *IO, error)
 }