Add initial SQLite-backed state implementation

This contains the implementation of (most) container functions,
with stubs for all pod and volume functions. Presently accessed
via environment variable only for testing purposes.

Signed-off-by: Matt Heon <mheon@redhat.com>

libpod/pod_internal.go

@@ -67,3 +67,10 @@ func (p *Pod) refresh() error {
 	// Save changes
 	return p.save()
 }
+
+// resetPodState resets state fields to default values.
+// It is performed before a refresh and clears the state after a reboot.
+// It does not save the results - assumes the database will do that for us.
+func resetPodState(state *podState) {
+	state.CgroupPath = ""
+}