Add version package

This PR adds a version package and consolidates version strings into a
Version struct.

client/driver/java.go

@@ -290,7 +290,7 @@ func (d *JavaDriver) Start(ctx *ExecContext, task *structs.Task) (*StartResponse
 		taskDir:         ctx.TaskDir.Dir,
 		killTimeout:     GetKillTimeout(task.KillTimeout, maxKill),
 		maxKillTimeout:  maxKill,
-		version:         d.config.Version,
+		version:         d.config.Version.VersionNumber(),
 		logger:          d.logger,
 		doneCh:          make(chan struct{}),
 		waitCh:          make(chan *dstructs.WaitResult, 1),