Add version information for all the components in machine spec

[puneetguptanitj]

Add support for adding version information for all the components and subcomponents in the machine spec. Will be required by actuator to determine which versions of components to use
Example state file

 machineList:                                                                                                                                                                                                 
   items:                                                                                                                                                                                                     
   - apiVersion: cluster.k8s.io/v1alpha1                                                                                                                                                                      
     kind: Machine                                                                                                                                                                                            
     metadata:                                                                                                                                                                                                
       creationTimestamp: "2018-08-04T19:49:15Z"                                                                                                                                                              
       name: 1.2.3.4                                                                                                                                                                                          
       namespace: default                                                                                                                                                                                     
     spec:                                                                                                                                                                                                    
       metadata:                                                                                                                                                                                              
         creationTimestamp: null                                                                                                                                                                              
       providerConfig:                                                                                                                                                                                        
         ValueFrom: null                                                                                                                                                                                      
         value:                                                                                                                                                                                               
           ComponentVersions:                                                                                                                                                                                 
             cniVersion: v0.6.0                                                                                                                                                                               
             etcdVersion: v3.3.8                                                                                                                                                                              
             etcdadmVersion: v0.0.1-alpha                                                                                                                                                                     
             flannelVersion: v0.10.0                                                                                                                                                                          
             keepalivedVersion: v2.0.4                                                                                                                                                                        
             kubernetesVersion: 1.10.4                                                                                                                                                                        
             nodeadmVersion: v0.0.1-alpha    

Depends on platform9/ssh-provider#39

[dlipovetsky]

LGTM