Update api proposal

Move concepts into specific files for easy management
Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@docker.com> (github: crosbymichael)

Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@docker.com> (github: vmarmol)

state.go

@@ -12,14 +12,33 @@ import (
 type State struct {
 	// InitPid is the init process id in the parent namespace
 	InitPid int `json:"init_pid,omitempty"`
+
 	// InitStartTime is the init process start time
 	InitStartTime string `json:"init_start_time,omitempty"`
+
 	// Network runtime state.
 	NetworkState network.NetworkState `json:"network_state,omitempty"`
 }
 
-// The name of the runtime state file
-const stateFile = "state.json"
+// The running state of the container.
+type RunState int
+
+const (
+	// The name of the runtime state file
+	stateFile = "state.json"
+
+	// The container exists and is running.
+	Running RunState = iota
+
+	// The container exists, it is in the process of being paused.
+	Pausing
+
+	// The container exists, but all its processes are paused.
+	Paused
+
+	// The container does not exist.
+	Destroyed
+)
 
 // SaveState writes the container's runtime state to a state.json file
 // in the specified path